Page:Popular Science Monthly Volume 2.djvu/327

Rh is objected, What has the power to establish such adaptation, except an intelligent being? We shall reply, that all those phenomena which are usually simultaneous in the organism have the power of suggesting each other, that is to say, of acting reciprocally as causes. They do in the end compose a circle, which vibrates throughout, whichever one of its links it may be that receives the impulse. Every gesture, every external movement of the body, is naturally followed by its perception, and consequently by its idea; by dint of being contemporaneous with the organic facts which determine the production of motion, the idea forms in connection with them habits of adaptation, the result of which is to give it the property of exciting them. Thus, the movement was at first involuntary, and theretofore it was the movement which stirred its idea in the intellect, through the intermediate means of perception; afterward the movement became voluntary, and it may be was caused, in its turn, by the cerebral phenomenon of its idea, which had had time to contract habits of coexistence, and of suggestion with the intermediate modifications of the nerves and the muscles. Such habits may even show themselves, so far as they are hereditarily reproduced and continued, as if they were innate with the individual.

It is the same with regard to those reflex movements which Hartmann also refers to an unconscious will and intelligence. He defines a reflex movement as "that which takes place when the excitement of a nerve of motion is transmitted to a nervous centre, which transmits it on to another nerve of motion, that produces in the last place a muscular contraction." This definition is evidently too broad, and would equally embrace all those movements that result from cerebral action; for the brain is also a nervous centre, which only transforms movements that come from outside of it, so as to transmit them to motor nerves. Physiologists usually confine the description of "reflex" to those movements as to which the series of facts intermediate between the external excitement received and the final act does not pass through the me, or the thinking brain. Now, among these movements, certain distinctions must be established. In a great number of them the most prejudiced mind could not discover any sign of finality, and therefore as to those there cannot even be any question of applying an hypothesis of an intelligence, whether conscious or unconscious; when, for instance, some one tickles me, and I laugh, I cannot recognize any thing between these two facts of laughing and of tickling, beyond an accidental and mechanical coincidence. Other reflex movements are very easily explained upon the hypothesis of natural selection; such, for instance, is the action of the spinal marrow on the