These unconscious reflex movements are in man of prime importance and frequency. The machinery of conscious movement is far more complex than that of reflex action, and every new cog-wheel, so to speak, involves a loss of time as well as of motion. Most of us do not appreciate the period of time between the willing and the making of a movement, yet the astronomer has to take note of it, and, finding that it varies in individuals, allows for the "personal equation" of the observer. We all recognize that one man is slower than another—i.e. that his physical machinery of thinking and doing moves more slowly than does that of his fellow. Every sportsman must have paralleled a little personal experience of my own. Last fall I shot at a flying quail between which and myself at the time of firing a sturdy oak tree raised its trunk. The bird was put up, aimed at, and the impulse sent by the will to the trigger-finger: before the impulse reached the finger I distinctly recognized that the bird had dodged behind the tree, but the countermand sent by the conscious will to the finger could not overtake the first order, and so, in defiance of my wishes, the gun was discharged.
There are many processes necessary to comfortable human life for which consciousness is far too slow in its operations. Had the eye to wait for conscious perception the dust which whirls in the air would soon blind it; but, as Nature has arranged the mechanism, when the speck approaches the eye the lid shuts instantly through a reflex act, even though the man be unconscious or sight has been lost. It will be noticed that in this movement of the eyelid a purpose is served: it is as though the man perceived the speck and willed to close the lid in order to protect the eye. An action done to serve an apparent end is spoken of by the physiologist as "purposive." It would seem at first that such an action implies consciousness, but it has just been shown that this—in regard to the eye, at least—is not the case, and before this paper is ended it will be demonstrated that adaptation for a useful end is no proof that an action is directed by consciousness.
If, instead of putting the feet of the prepared frog spoken of a few paragraphs back in acidulated water, we drop the irritant upon the thigh, the corresponding foot is raised at once and bent upward so as to brush off the acid. If the foot has been cut off, the bleeding stump will still be bent upward, and if it be too short to reach the irritated spot, then the other foot will be raised and a determined effort be made to remove the offending liquid. All these movements certainly look as though the frog felt the acid and endeavored to get rid of it. Not so, however. Drop this same frog into water which is gradually heated. The batrachian does not try to get out, but sits motionless until he is boiled. Surely, if he felt the drop of vinegar on his foot, much more would he feel the boiling water bathing his whole surface. Curiously enough, if the acid be put upon the leg of the frog while in the water, the movements will be the same as if he were on the table.
These experiments and the experiences of daily life clearly show the truth of the assertion recently made, that the fact that an action has a purpose does not prove its connection with consciousness. If Evolution be correct, there is no difficulty in explaining the doings of the beheaded frog. It is a law governing nervous function that every time an action is repeated the tendency to repeat the action is increased, until at last habit becomes a governing law, and under certain circumstances actions, at first wilful, become unconscious. The first earth-born batrachian, perhaps, felt during the first hour of his existence some irritant on his leg and scratched it away. The next hour the process was again gone through, and so on until the frog was gathered to his fathers. His children found themselves a little more disposed to scratch than was their progenitor; and at last, so well accustomed did the spinal cord become to move the feet when the irritant touched the leg that the motions were carried out without waiting for the will to command, and the particular reflex movements which astonish the late-born human philosopher became a fixed habit.
In such movements as have been described are to be found the simplest form of automatism, the term being used to express the doing of actions which are performed for an end, but in which consciousness plays no part.
Having studied the spinal marrow, the physiologist, leaving this untouched, cuts off the upper brain of the frog, leaving the lower brain in union with the spinal cord, and unharmed. A frog so mutilated, sitting upon a leaf or tuft of grass in a swamp, would be apt to be passed unnoticed as anything extraordinary. He sits perfectly still when approached, but touch him and he leaps off vigorously. If an obstacle be in the way, he does not strike it, but springs above, below or to one side as circumstances may favor. If dropped into the water, he swims as well as ever, and if the water be gradually heated, he soon endeavors to get out. If, as he sits upon a board, the latter be quietly and not too suddenly moved, he does not jump away, but continually shifts his position, so as to maintain the centre of gravity in its proper place and to keep the normal erect posture. Stroke the back of the frog gently and he croaks responsively, as if the titillation called back pleasant memories of caresses received in some lover's tussock-bower. The answer to the stroking is so certain that, as suggested by Goltz, a chorus of brainless frogs might be obtained whose batrachian voices would delight the nerves of old Aristophanes with a triumphal burst of Brekekekéx! koáx! koáx!
Many other things will the brained frog do—almost enough to convince a superficial observer that the cerebral hemispheres are a luxurious superfluity to the physical and mental well-being of the average inhabitant of the swamp. But no. A little watching shows that for this seemingly intelligent creature past, present and future are alike blotted out. Let the frog alone and it sits motionless, buried not in the profundity of its thoughts, but in the abyss of its thoughtlessness. In the midst of abundance it starves—not, like Tantalus, because it cannot gratify its desires, but because it has no desires to gratify. It feels no hunger, or if it feels hunger seeks no food. A perfect automaton, it moves when touched, it croaks when stroked, it answers to a multitude of external irritations, but when untouched and left to itself it is as a lifeless clod until the sun dries it up and the winds blow it away.
The fish whose cerebral hemispheres or upper brain has been taken away has, like the frog, all conscious perception blotted out, but, unlike the frog, it is in perpetual motion. Stopping not for food, it rushes through the water, avoiding obstacles, but never ceasing its mad race until muscle-power or nerve-force fails because of excessive use and lack of nourishment.
The cerebral hemispheres can also readily be removed from birds. The pigeon so mutilated presents phenomena similar to those offered by the frog. He remains perfectly quiet, balancing himself readily on his perch, but with drooping eyes and sunken head, motionless so long as undisturbed. Move his perch, and he struggles to maintain equilibrium; fire a pistol near him, and he starts, only to fall back at once into his apathy; approach him in the dark with a bright light, and he gazes at the candle with a fixed stare, and sometimes follows its movements with his head; strike at him from the front, and he will draw back; pinch his toes, and he moves. It is therefore plain that he in a certain sense sees, hears and feels. Yet when perishing with hunger he never pecks at the corn which he sees placed before him, and if left alone dies. If, however, the food be placed in his mouth he swallows it eagerly, and by care can be kept alive for an indefinite period.
Removal of the cerebrum has been repeatedly practised also upon the rabbit and the guinea-pig. The mutilated rabbit sits motionless whilst undisturbed, starves in the midst of plenty, cries out with its peculiar pathetic scream when pinched, draws back when ammonia is put to its nostrils; in a word sees, hears, feels in the same sense as does the pigeon, and, like the pigeon, undisturbed remains passive until death. Tread, however, upon the rabbit's foot, and perhaps with a little scream it darts forward in a furious race. Once started, it, like the brained fish, does not stop until exhausted or until it has dashed its head against some obstruction, for, unlike the mutilated fish, it does not have the power of avoiding obstacles.