8 THE FOUNDATIONS OF ZOOLOGY 



apprehension if it be thereby supposed that the brain is the only 

 organ which is concerned in the function of mind. There is not 

 an organ in the body which is not in intimate relation with the 

 brain by means of its paths of nervous communication, . . . and 

 which does not, therefore, affect more or less plainly and specifi- 

 cally its function as an organ of mind. It is not merely that a 

 palpitating heart may cause anxiety and apprehension, or a dis- 

 ordered liver gloomy feelings, but there are good reasons for be- 

 lieving that each organ has a specific influence on the constitution 

 and function of mind ; an influence not yet set forth scientifically, 

 because it is exerted on that unconscious mental life which is the 

 basis of all that we consciously feel and think. Were the heart 

 of one man," says Maudsley, "to be placed in the body of another, 

 it would probably make no difference in the circulation of the 

 blood, but it might make a real difference in the temper of his 

 mind. So close is the physiological sympathy of parts in the 

 commonwealth of the body, that it is necessary, in the physiologi- 

 cal study of mind, to regard it as a function of the whole organ- 

 ism, as comprehending the whole bodily life." 



A most notable illustration of the way a complicated adaptive 

 mechanism may be thrown into beneficial response by a physio- 

 logical stimulus, is found in the shad, which, when its bodily 

 structure is excited by the reaction of approaching sexual matu- 

 rity, leaves its home in the ocean and enters upon a journey 

 which, before its path was obstructed by dams, carried it across 

 the broad states of Virginia, Maryland, and Pennsylvania, to its 

 spawning ground in central New York. 



The excitement of adaptive vital changes in one part of the body 

 by changes in another part is not restricted to the channels afforded 

 by the nervous system. Florists make their plants bloom before 

 their time by confining their roots in small pots. The seeds of an 

 apple are new beings, but the apple itself is part of the substance of 

 the mother-tree, yet the blossoms will not set fruit unless they are 

 fertilized. 



When a duck's o.^^ is put under a hen, it undergoes a long series 

 of wonderful changes, which all prove, in the end, to be in respon- 

 sive adjustment to the normal life of ducks ; and as the production 

 of a duck by the mere heat of a hen, or that of a lamp in an incu- 



