[Certain students] suppose that because science has penetrated the structure of the atom it can solve all the problems of the universe. ... They are known in every ... college as the most insufferable, cocksure know-it-alls. If you want to talk to them about poetry, they are likely to reply that the "emotive response" to poetry is only a conditioned reflex .... If they go on to be professional scientists, their sharp corners are rubbed down, but they undergo no fundamental change. They most decidedly are not set apart from the others by their intellectual integrity and faith, and their patient humility in front of the facts of nature.... They are uneducated, in the fullest sense of the word, and they certainly are no advertisement for the claims of science teachers.

A bird maintains itself in the air by imperceptible balancing, when near to the mountains or lofty ocean crags; it does this by means of the curves of the winds which as they strike against these projections, being forced to preserve their first impetus bend their straight course towards the sky with divers revolutions, at the beginning of which the birds come to a stop with their wings open, receiving underneath themselves the continual buffetings of the reflex courses of the winds.

If we denote excitation as an end-effect by the sign plus (+), and inhibition as end-effect by the sign minus (–), such a reflex as the scratch-reflex can be termed a reflex of double-sign, for it develops excitatory end-effect and then inhibitory end-effect even during the duration of the exciting stimulus.

It is distinctly proved, by this series of observations, that the reflex function exists in the medulla independently of the brain; in the medulla oblongata independently of the medulla spinalis; and in the spinal marrow of the anterior extremities, of the posterior extremities, and of the tail, independently of that of each other of these parts, respectively. There is still a more interesting and satisfactory mode of performing the experiment: it is to divide the spinal marrow between the nerves of the superior and inferior extremities. We have then two modes of animal life : the first being the assemblage of the voluntary and respiratory powers with those of the reflex function and irritability; the second, the two latter powers only: the first are those which obtain in the perfect animal, the second those which animate the foetus. The phenomena are precisely what might have been anticipated. If the spinal marrow be now destroyed, the irritability alone remains,—all the other phenomena having ceased.

It seems to me that you are solving a problem which goes beyond the limits of physiology in too simple a way. Physiology has realized its problem with fortitude, breaking man down into endless actions and counteractions and reducing him to a crossing, a vortex of reflex acts. Let it now permit sociology to restore him as a whole. Sociology will wrest man from the anatomical theatre and return him to history.

Plants are extraordinary. For instance ... if you pinch a leaf of a plant you set off electrical impulse. You can't touch a plant without setting off an electrical impulse ... There is no question that plants have all kinds of sensitivities. They do a lot of responding to an environment. They can do almost anything you can think of.

Reflexes and instincts are not pretty. It is their decoration that initiates art.

Some say that everything that is called a psychical law is nothing but the psychological reflex of physical combinations, which is made up of sensations joined to certain central cerebral processes... It is contradicted by the fact of consciousness itself, which cannot possibly be derived from any physical qualities of material molecules or atoms.

The development of mathematics is largely a natural, not a purely logical one: mathematicians are continually answering questions suggested by astronomers or physicists; many essential mathematical theories are but the reflex outgrowth from physical puzzles.

The Law of Inhibition. The strength of a reflex may be decreased through presentation of a second stimulus which has no other relation to the effector involved.

The nervous system is the most complex and delicate instrument on our planet, by means of which relations, connections are established between the numerous parts of the organism, as well as between the organism, as a highly complex system, and the innumerable, external influences. If the closing and opening of electric current is now regarded as an ordinary technical device, why should there be any objection to the idea that the same principle acts in this wonderful instrument? On this basis the constant connection between the external agent and the response of the organism, which it evokes, can be rightly called an unconditioned reflex, and the temporary connection—a conditioned reflex.

The role of inhibition in the working of the central nervous system has proved to be more and more extensive and more and more fundamental as experiment has advanced in examining it. Reflex inhibition can no longer be regarded merely as a factor specially developed for dealing with the antagonism of opponent muscles acting at various hinge-joints. Its role as a coordinative factor comprises that, and goes beyond that. In the working of the central nervous machinery inhibition seems as ubiquitous and as frequent as is excitation itself. The whole quantitative grading of the operations of the spinal cord and brain appears to rest upon mutual interaction between the two central processes 'excitation' and 'inhibition', the one no less important than the other. For example, no operation can be more important as a basis of coordination for a motor act than adjustment of the quantity of contraction, e.g. of the number of motor units employed and the intensity of their individual tetanic activity. This now appears as the outcome of nice co-adjustment of excitation and inhibition upon each of all the individual units which cooperate in the act.

The true-spinal system consists of a series of nerves passing principally from the cutaneous surface, and the surface of the mucous membranes, to the spinal marrow; and of another series of nerves passing from the spinal marrow to a series of muscles, destined to be moved simultaneously. The former, thence designated the incident nerves; the latter, reflex nerves: the spinal marrow is their common centre.

With the nervous system intact the reactions of the various parts of that system, the 'simple reflexes', are ever combined into great unitary harmonies, actions which in their sequence one upon another constitute in their continuity what may be termed the 'behaviour'.