OF I AND IT12 [204]

W.S. McCulloch

Introduction

But let one man read another by his actions never so perfectly, it serves him only with his acquaintances, which are but few. He that is to govern a whole Nation, must read in himself, not this, or that particular man, but Mankind: which though it be hard to do, harder than to learn any Language or Science; yet, when I shall have set down my own reading orderly, and perspicuously, the pains left another, will be only to consider, if he also find not the same in himself For this kind of Doctrine, admitteth no other Demonstration.Thomas Hobbes, Leviathan

Let us discuss a problem involving the use of words in communication of patients with doctors. I am associated with the Research Laboratory of Electronics (R.L.E.) of the Massachusetts Institute of Technology. The reason why I work there is that it is concerned with problems of communication, not merely in terms of circuit action, its physics and chemistry, but also with signals themselves as conveyors of information. Many members of R.L.E. have to estimate the quantity of information that can pass through a given noisy channel and therefore must distinguish between signals, which are true or false, and noise, which is neither. Thus signals have not merely the properties of physical eventsphysical propertiesbut also those properties characterizing communication of propositionslogical properties. This holds even for those least signals out of which complex ones are formed. Communication is best conceived as the enunciation of significant propositions, that is, as the saying or sending of a sentence asserting that such and such is the casetrue if it is the case, otherwise false and often lost in the noise that makes it indistinguishable from other sentences. Man is a noisy channel. He corrupts information. Phonemes and morphemes convey information in this technical sense, for each one exercises a selective function upon the total ensemble of possible messages. But it would be a mistake to suppose that either a morpheme or a phoneme has one meaning.

The meaning of a sentence in any language is the class of all sentences in every language which are true (or false) in the same set of cases. Thus the meaning of a sentence is a proposition. A single word, except when it is a sentence, does not have a meaning. Yet it does affect one who sees, hears, or thinks it. It may produce a response or alter the way in which he responds to other words. If it alters his response, it is clear that the effect produced by each word depends upon the other words in the combination. In this sense, as MacKay says, it alters the transitional probability of his implicit or explicit behavior. If we want to speak of the meaning of a word in general, it would have to be defined in terms of the effect it has in all possible combinations in languagesand these effects are many, not one! Hence, in the sequel, do not look for the meanings of the nouns consciousness and self-consciousness or of the pronouns I and it. Note only how the former are used in this description and the latter by yourself and your fellow men.

To the members of an established society, in questions of manners, morals, and the common law, ignorance is no excuse. They are matters of use and wont and could not exist but for a knowledge of them common to the community. Of the res communis they are the very res conscientia. So consciousness is conceived, in a social setting, as common knowledge.

In Roman lawfor example, in the trial of Christthe testimony of a solitary witness was without weight in evidence. The judge charged the witness to let his conscient be his guide. It required two witnesses to the same event to be conscious of it.

In forensic medicine, the policeman who finds the man in the ditch and the doctor who attends him in his bed apply the same test: they tell the judge or the jury that the man was then and there conscious if he can bear witness to those things to which they also can bear witness. If not, he was unconscious. It is thus that we use the term.

Contrast with this, if you will, Abelard's res conscientia for constructive classes, and Spinoza's, for the ideas of ideas. These usages are familiar in introspective psychology and in some philosophy. They are not social usages. The events embodying them can occur, and Walter Pitts and I have proposed circuit actions to embody them, in a single head. They are interesting notions but unnecessary in our context.

The history of the term conscience is more to the point and a warning against the use of consciousness, or worse, subconsciousness, as synonymous with Galileo's mind stuff and the ghost of his mind stuff. Thomistic doctrine holds that God knows us even as we know ourselves, that is, substantially. Hence the dying word of a Christian is to be believed if he cries, God is my conscient that such is the case. Self-conscious in this substantial sense has a Silent Parmer who may be forgotten. When He is, conscience and self-conscious drift into social contexts as synonymous with some form of an excess of subjectivity. conscience, as morality or its Freudian inversion, becomes a matter of conformity to some accepted opinion others have of us; and self-consciousness acquires the flavor of being ill at ease in society.

When I speak of substantial knowledge, I have in mind that knowledge which one has of himself because he is the this one that has it. I need no excuse for using substance in this sort of Aristotelian sense in a philosophical context, for I am sure you will not think of chemical substances or the wealth of solid citizens. Of everything but himself a man has only objective knowledge; that is, he has sensations or perceptions which he projects as those, there, then. By subjective knowledge of one's self I mean what one infers concerning himself by observing how his actions affect the world around himincluding other people. I am aware of the present trend of social sciences to deny substantial knowledge entirelyand suppose only the subjective. There is something to be said for this notion, but it goes too far. I am also aware of a still stranger reason for denying substantial knowledge, for, if we include all actions of our bodies among things known objectively (call them sensations, feelings), there is little left to account for substantially. Yet, do what we will, something remains that cannot be completely ignored. Perhaps it is this that underlies what my children call the foolish question: How come, of all the me's there arc in this world I'm this one?

Helmholtz says that, in observing, one has to reduce himself to the mere locus observandi. Einstein echoes this and enlarges it to the inescapable frame of reference of the observer. Bertrand Russell stumbles upon it as the ineluctable egocentric particular involved in all descriptions, for someone must point at something. Donald MacKay, in his papers on information theory of science itself, is compelled to distinguish between the language of the actor and that of the observer of the act. The very pronouns I, me, mine bespeak this core of substantial knowledge. The notion is reflexive and best represented by a picture of a man pointing at himself. He stands at the point whence he observes himself in his frame of reference, and he is at the point whither his action points at himself to describe the meaning of this is me. This makes it clear that every man is for himself one part of his known world. It even makes it clear where that part is situated.

Immanuel Kant says, I believe correctly, Each of us arises for himself as a proper part of his known world, thereby emphasizing, as a scientist should, the role of knowledge in the ontogenesis of the empirical self. Our knowledge is derived from our sense organs by way of nerves conveying impulses to the central nervous system. These organs, commonly called receptors, can be divided heuristically into those that report impressions from the world about usexteroceptorsand those that report the state of our bodiesproprioceptors, nociceptors, and so forth. Here we must be very careful not to oversimplify the description. We are apt to think that sensations in the other fellow are situated at those places in his brain to which the nervous paths convey sensory impulses. In a sense, this is necessarily true. But we can only judge whether or not the sensation occurred in him by observing some output from his brain. Speech is only one such channel and fails us in the majority of cases. Even the trained subject frequently responds differentially, although introspectively he cannot detect any sensation to which he can ascribe his decision. In most of our instinctive and highly skilled performances, as long as they are moving swiftly and smoothly, we are simply not aware of anything except those significant differences in our environment that demand special adaptations. Only these claim our attention, and it is only of these that we can bear witness that is, it is only of these that we are potentially conscious in the social sense. Note, please, that these potentially public events are those that he outside the body of the actor. All of his sensations, properly speaking, are within him; and the bulk of those that he derives from within his body (his feelings) are doubly private, for their origins and terminations are beyond our preview. I say the bulk, for in the practice of medicine, especially surgery, we do invade that privacy and so do discover something of the internal events of which our patients complain.

From this we learn slowly that we must translate the symptoms from the spoken word of the patient into a language much more closely related to our own sensations, and from this imaginary construct we must again translate them into the terms of pathological anatomy and pathological physiology which describe the state of a body with those sensations. It is impossible to overemphasize the necessity for the doctor, particularly the neuropsychiatrist, to listen through the words to the experience of his patient, and to look through that experience to a mental picture of the events in that nervous system. This will become clear in considering the self-consciousness of patients, their use of I, me, mineas opposed to it. In bedside diagnosis this difference is often decisive. But that is only said here by way of caution. We have another point to clear up before we can pass from Aquinas or Kant to the clinic.

All nervous impulses, including those from our receptors, are signals in noisy channels. For our purpose, it makes no difference whether the information conveyed by these signals is coded into that nerve fiber which has the impulse, or into the intervals between pulses in a given fiber, or in some other way. Each bit of information is conveyed by some event that either happens or does not happen. To convey that bit, the event in question must be one of some particular class, and any member of that class must occur only if the event it represents did occur .When the later event occurs without the earlier having occurred, it is a false signal. Nervous systems do suffer from false signals, that is, events that propose events that did not happen. When your foot goes to sleep, you sense pins and needles that are not in your foot. When you hit your funny bone, you feel things in your little finger that arc not happening there. When you press your eyeball, you see a light where there is not light. When you get a blow on the back of your head, you see stars. If you have an abscess over your liver, you are apt to feel the pain under your shoulder blades, and if you have trouble with your heart, the pain is often in your left arm and left hand. In short, the events somewhere in your brain may propose events somewhere in the world around you or in your body when those proposed events did not occur there. Normally you can trust your sensations, for normally they do imply the events that they propose. So you project them upon your frame of reference, thereby possessing objective knowledge of that world, including your body.

What about your brain? No sense organs have been found in it. You have no direct objective knowledge of your brain. In this sense your brain, the organ that is doing the sensing, is for you only a logical construction, if it is even that. Hence you must be content to suppose either that you are ignorant of your ideas and intuitions, your hopes and fears, or else, one of two things: either you infer them from what you see happening in the world and in you as a result of your actions, or you infer them from sensations from your own body (your feelings). Or perhaps from both. No, this will not do. One does have knowledge of his own brain's doings because it is his brainnot, of course, of where certain neurons are active or of the patterns for projected sensations or for intended acts, but our ideas, perceptions, sensations, and intentions themselves are known to us. Perhaps not as often as we may suppose, but potentially, when we have leisure.

For each man there is a vagrant solid, called his body, part of which is his brain. Let him be a philosopher sitting comfortably in his chair, and let me ask him, not where he is, but what vagrant solid he means by I and he will point at himself. Being a philosopher he may even point at his head, and he will probably have in mind especially the collection of his thinkings and intendings that go on in his brain. That is the only vagrant solid of which he has substantial knowledge, and only substantial knowledge, though his brain is for him only an imaginative construct. Let me assure you that, while I have no quarrel with him as to his notion of himself under these circumstances, the vagrant solid he calls I will change from moment to moment as he goes into action. The question I shall try to answer is concerned with that changing vagrant solid. I shall try to make clear what quality of an event causes it to be included within the vagrant solid we call I, me, mine, and, conversely, what quality causes its exclusion from ourself as a mere it. I will do this on the basis of the way men use these pronouns, in vigorous life and in disease. I am not talking of that of which we have substantial knowledge but of the self as a part of the known world.

This is the thesis. Those events that occur as intended may be experienced by the actor as I, me, mine; all else, as it.

Even our philosopher who just pointed at himself would say quite naturally, I pointed at myself. The finger, hand, and arm he used in pointing are parts of the vagrant solid I that did the pointing. So it is clear that even he, when he is in action, by I means more than his ideas and intuitions. Substantial knowledge has located the egocentric particular in its frame of reference and labeled it I in the language of the actor but has not bounded the event of the empirical knower. Suppose, just when our philosopher intended to point at himself, his hand had metamorphosed into a butterfly that lighted on my head. He might well have said of that butterfly, It's very pretty, but it's not my hand and it's not doing what I intended. The experience might seem strange to him, but it is not as uncommon as you may suppose. Many a man wakes in the night to find something lying across his face and throws it off only to find it attached to his shoulder. Not until it moves again as he intends does he feel it as his arm.

If our philosopher is in love with wisdom he probably was not thinking about himself until I asked him, and he probably was not aware that it was he that was pointing at himself until I challenged him. That is why I say that all events occurring as intended may be experienced as I, me, mine, instead of saying that they are so experienced. Obviously a man is not aware of himself. It takes a challenge of some sort to make him think I. Let us invade the kingdom of the absolute monarch with the question What is the State? and the answer Ltat, c'est moi. Let me, as the physician, have the king cross his legs and let me strike his patellar tendon with a reflex hammer, thereby eliciting his knee jerk, and, looking sharply into his face, ask Did you kick? He answers, No. It kicked. So do you, unless you are hostile; then you say, No. You made it kick. If you doubt this, try it on your unsuspecting friends.

But the neurological clinic is replete with better examples. The first chief complaint I ever recorded verbatim was that of a little Britisher who stood bolt upright in front of me when I asked his story and answered, I went into Afghanistan, thirty men well armed and well appointed. I came out three men at death's door. Since then something has always been wrong. What? said I, and he answered, pointing at his left shoulder, That arm. It had been paralyzed by a shot through the neck. I, thirty men; I, three men are Ltat? C'est moi. No doubt his men obeyed him; and the arm that did not was not my arm but that arm.

In Bellevue hospital I examined over a hundred cases of sudden organic paralysis, and every one of them referred to the paralyzed part as it, even when sensation was normal in that part.

So the vagrant solid called I can extend to a whole kingdom, or to a detail of thirty, or three, men; and it can shrink to less than the body of the monarch or the officer when the part ceases to obey. Thus their language does express what they experience at that time.

Let me tell you the illuminating story of my patient Donovan, now deceased. He was wheeled into my ward where he told the following story. Come three weeks Sunday, I am putting a canvas top on a car in my cellar and I needs more canvas and I goes to get it and I sneeze like hell and both legs give way under me and I hauls myself to a barrel and onto it, and the wife comes down and sees me sitting there and says What do you think this is? A Holiday? and gives me a push and over I goes. Then she gets scared and calls help, and my wife and my neighbor carries me to bed and for two weeks I can't get up 'cause it hurts like hell.'’ Notice that he said I'’ of his intended acts, his sneeze, and his getting to and onto the barrel; but it was the legs that gave way. Notice, it is the wife when she nags and upsets him but my wife and my neighbor when they carry him to bed. And now comes the most surprising point: I can't get up, not because the legs were paralyzedthey werebut because it hurts like hell. When I heard the end of this history I began to wonder what I can't expressed by way of experience.

Some years before I had learned the maxim of petty officers in the navy: If a man says I can't knock him down, if he says She's fast bare a hand. I had thought that a man saying of himself I can't was thinking of himself instead of his job, but now the maxim took on new meaning. I examined a large number of patients who had some limitation of motion at a joint caused by a painful process, like arthritis. All could move the joint; all said I can't; and when pushed for an explanation, all said because it hurts. The limitation of action produced by pain is this: pain puts a limit on the self, experienced as a change in oneself. It prevents one from wanting to do what is required of him. An experience of this kind should be detectable in ordinary life, and it is.

There is probably no man in this audience who could not and would not single-handedly toss a grand piano off his girl if it fell on her; but most of you, if I merely asked you to lift it clear of the floor, would answer I can't and, if you tried to, would experience I can't. In short, the I can't is really a way of saying I don't want to enough to pay what it costs. It is an experience quite different from that of a man who merely knows that it is too heavy.

If you have ever been sick abed long enough to be enfeebled or if you listen to a man who has had a paresis, a weakness, you will note that what has happened is that things have become heavy .We make the effort and the results fall short; the change seems to be in the world, not in ourselves.

The patient with pain, and the hysterical patient who, for some reason, does not want to stand or walk or lift something, does not say the legs don't move or it's heavy, but I can't stand, I can't walk, I can't pick it up. In a sense both have failed to project their difficulties out of themselves onto the it beyond themselves. Sensations are normally projected. Pain is the exception because it so affects us that we sense ourselves as altered by it. This kind of challenge can and does make us think, and sometimes speak, of ourselves. Sometimes!

Per contra: consider a carpenter nailing boards on a roofhis hammer eventually comes down on his thumb. Normally the good hammerman curses the hammer and goes on nailing. If it hits his thumb again he may throw the hammer over the ridgepole, but when you toss him yours he goes on nailing. He has successfully projected the unwanted action onto the hammer and not blamed himself. He is a good naildriver. Had he come off the roof saying, I hit my thumb, you would have paid him off and sent him home or to the doctor, not for the damage to the thumb but for being diverted from his job to attend to himself. You don't want a man who can't nail because his thumb hurts him. So-called paranoid conditions have this natural projection at their core. They are diseases only because the patient is overly aware of failures that he blames on others. We all fail by falling short of what we intend, but the paranoid has a greater discrepancy between what he desires and what he achieves. When he ceases to blame others, he is often depressed or suicidal (the former if his anger cools, the latter if its object changes). In either case he is actually aware of himself, and it is a pathological self, yet still that vagrant solid that did what he intended to do, only now he does not approve of it. It is always possible to think I was wrong, for that is mere history. It is practically impossible to think I am wrong and still hold that opinion, or intent, for that is tantamount to a contradiction. To say I am wrong is really to say I am already of a different opinion. As I said earlier, this is the sort of verbal affair through which one has to look carefully for the experience of the patient. The depressed despairs of correction; the suicidal would destroy the offender whom he cannot change; but neither applies the same test to the concurrent self that he does to the remembered or imagined self.

Thus far we have looked at the vagrant solid self as limited, on the motor side, to the events we can control, and at the limits set by pain and suffering upon that control. Let us look next at the sensory side, other than pain.

From the very nature of sensation it is obvious that no one is directly aware of his ignorance. We do not see our blind spots. A man with a tumor or injury of the pathway from his lateral geniculate to his visual cortex or of the cortex itself, simply does not see anything in the corresponding portion of the visual field. He blames people, or lamp posts, for walking into him. On the other hand, if he loses his eyes themselves, as from wood alcohol, or even temporarily, as in fainting when the circulation fails, what happens to him is that the lights go out. If you will look again at Milton's Samson Agonistes, you will discover that Samson is blind by loss of his eyes, even as Milton was, for he is in the dark. But Samson was also paralyzed; yet he neither experiences his arms and legs as it, nor has his world grown heavy. He simply can't do this and that: This is a hysterical paralysis. Perhaps that is what Milton intended, but I suspect that Milton, who was not paralyzed or paresed, had no idea of what such a patient experiences.

The story of sensation may be clearer on the side of vision than elsewhere because we can direct our gaze whither we will and close our eyes when we want to. It is clearly a voluntary act of which we usually say I see. All other sensory modalities we can at most ignore, and pain we cannot quite shut out when it is strong. Rather typically we say it hurts me. We similarly say of too much fight that it blinds me. Carrying the same theme a little beyond sensation, to struggle of all kinds, we are apt to say it beats me. So me, as something often put upon or overcome, differs from I, not merely grammatically but by standing for those events that are limited by it rather than extending to include all events dominated by our intentions. mine refers chiefly to the realm in which our dominion is less than absolute. We may assert it of our own hands, but only when the simple possessive my is challenged. The strangest complaint I have ever heard from a neurological patient was, the eyes don't see. I have heard it twice. Both times the patient had a sudden onset of a coarse vibration of the eyes. What makes it so strange is that the trouble on the motor side, making the eyes out of my eyes, has upset the vision which, being on the sensory side, is a kind of blindness that is not ocular (the world not black) nor central (not just blank) nor hysterical (not I can't).

We have had to consider hysteria because it is forever caricaturing neurophysical disorders and has to be separated from them in every clinic. There are some neurotic patients who complain of some of their actions as alien to themselves, as thus: Doctor, when I heard her story my eyes wept, but I was not really sad as all that, so I feel as if it was not me weeping. This is sometimes called neurotic depersonalization. Contrast it, if you will, with a patient suffering from athetoid movements or hemiballismus, say in his left arm, who says, Cut that damn thing off. It gets in my way and it keeps me awake. The neurotic suffered only a weakening of sensed affect; the other, a disobedient member. But there is another condition also called depersonalization which occurs in catatonia. The patient may be standing next to a steam radiator and his shins burning, so you say to him Hey, don't you know your shins are burning? and his slow answer comes back, Yes. Doesn't it hurt? It hurts. Well, why don't you step back? and he points slowly toward his head and says It doesn't seem to care. So from him with the caring, with the intending to do anything about it, the I has also evaporated.

Finally, look briefly at hallucinations, not extracampian or other pseudohallucinations like a small ball of Are four inches behind the head, for such a group of words is never to be mistaken for a description of any sensory experience, but such hallucinations as epileptics have. These differ little from ordinary visual or auditory or other sensations or vivid memories of them, except that they come unexpectedly in a way that is out of harmony with everything the patient knows about his sublunary world. They are often called hermeneutic experiences, as if the messenger of the gods had brought them from beyond the empyrean. They seem to the patient to be obviously it, not I; yet he knows, as a reasonable man, that the events responsible for them lie within his brain. Now a man may be able to imagine the scene or recall a voice quite as vividly at will. Under these circumstances he merely refers them to his imagination or his memory. Vivid dreams are their normal equivalents in us, and we also can recall them at will as our own, although when we dreamed them they were alien enough. Again the distinction lies in our intending to recall the hallucination or the dream instead of its happening to us willy-nilly. In fret, I doubt whether there is a great difference between our fancy, our imagination, our memory, our dreams, and even our hallucinations except the intention to have them. Perhaps the reason we call our memories our own is that we recall what we will. Somnambulisms, that is, experiences in which people relive some portion of their past as if it were here in the now, are characteristically of an unpleasant content, It and Not my fancy. So these more complicated psychological affairs are also in line with the thesis that whatever we experience as intended we may experience as I, me, mine, and all else as it.

If you walk out into a cold rain you know where you end, and it, the wet collar, begins at your neck. The line between you and it is very sharp. But he under a cool tree on a summer day, want only a glass of beer and there it is, and try to be sure where you end and it begins. The line has grown very fuzzy. Typically we say you pinch yourself to be sure you are awake. Hence the old expressions Too good to be true and Too beautiful to live. Thus the scientist suspects himself and is never completely happy until he again walks into a door in the dark. Listen to Urey: I am never happy with a theory until it leads me into a flat contradiction with a fact. Then I know I had a theory. Let us therefore look at several kinds of experience in search of that contradiction.

Many people who have had the aesthetic experience have described it in many ways. There is the Hegelian the idea and the thing become one. There is sympathy or empathy in which one feels as he would if he were it, and so on. All clear descriptions point to a lack of boundary between I and it. The religious experience goes farther in the same direction, for what is sacred or holy so engulfs us that we lose ourselves in it. In the mystical experience the division between ourselves and the universe evaporates. This produces agnosia, that gnostic experience which, however emotionally intense, is devoid of content; for in it nothing specific is known. But certainly the most familiar of such experiences is that of being in love. Spinoza would have it that the self expands to include the beloved, even when it is God who is loved. Schopenhauer would romanticize it into the subordination of one's self to his beloved. No matter how different these expressions, both hold that at the core of love is the union of two selves. The experience is most intense at the moment they merge, or, as Maloy says, meld, when the two, I-you, changes into the one, we. Its intensity depends upon the sharpness of the original sensation which gives it its tang and on the completeness of the union, which makes of me and mine, we. Had the beloved, the moment before, said No, had society said No, the separation would have been very sharp and the tang clear.

The lover would have felt keenly the reality of his beloved and of the whole situation; but if she is agreeable and society smiles upon the union, sentimentality requires a relish to spice the dish and so keep it intensely real. This can be done by making it hurt one's self (masochism) or hurt her so that she withdraws and must overcome it (sadism), or by that funny mixture, the lovers quarrel, whose tears water its kisses of reconciliation. Sex, being with us less urgent than hunger and thirst and respiration, gives us the leisure to distort it with more of our notions; but these, its proper sentimentalities, are sufficiently explained by our thesis and do not require the elaborate interpretations put upon them by psychoanalysis.

To know the beautiful, the holy, the universe, or even my lady, in the sense of being one with them, is to know even as a scientist knows his little domain of data. If you ask him what he means when he says that something is real, he will tell you that it is real if it goes by some law of its own! But his test remains like that of the self-distrustful sentimental lover. He is sure that it is love, and not just his invention or his fancy, only when it goes against him. Hence Urey's liking for a theory only when it leads to experimental refutation, for then he knows he has a theory. When the scientist embraces his world with this love of stubborn fact, he comes to know that world so well that his fancies and his theories conform to its ways. This, in a sound body, is a prescription for humble sanity leading perhaps to nirvana, though we be still a long way off.

I have presented to you a theory and indicated that it is based on some evidence. The most that any man may ask of his theory is that it conform to some body of data. It is a theory of consciousness and self-consciousness so devoid of pseudo-problems that I can specify circuits to perform what I propose. These terms are used in their social sense of the agreement of witnesses. According to Einstein, the community of agreement reached by taking into account the observations and the relations of the observers comprises the truths of science. Clearly they are truths for the epistemological knower, the communion of scientists, not for the empirical knowers, the members of that society, in their private lives, private sensations, and doubly private feelings. Yet from the use of I, me, and mine in the communications of daily life in health and disease, we are entitled to infer that the vagrant solid which the speaker calls 7 in the moment of experience consists only of events that occur as he intends. The rest he calls it. It is real because it goes against him. The good may be nebulous, but the evil is always real. In presenting this thesis to you as an invasion of communication theory into psychology and philosophy, it is my hope that it will sooner or later encounter evil, namely, a flat contradiction in fact. Only such a flite will prove that it was not a pseudologia fantastica but the theory I intended it to be. I commend it to you for refutation.


1 Reprinted from Perspectives in Biology and Medicine, pp. 547-560, Vol. 12, No. 4, Summer 1969.
2 This work was supported by the National Institutes of Health Grant 5 ROI NB-04985-06.