84 



ANIMAL MECHANISM. 



We seek at the present day to state with precision the rela- 

 tion between causes and effects, to ascertain the gradual transi- 

 tions which the animal or vegetable organism is able to pass 

 through when it finds itself placed under new conditions. 

 We have a glimpse of the influence which function exercises 

 over the organ itself which produces it. The short and pithy- 

 formula of Mons. J. Guerin, ^'Function inahes the organ,^^ ex- 

 presses in a general manner the modifying action of function. 

 This formula will acquire additional force when supported by 

 individual examples. 



It must be shown how the bones, the articulations, the 

 muscles are modified in various ways by the effect of func- 

 tions of different kinds ; how the digestive apparatus, yielding 

 to very varying kinds of food, passes through transformations 

 which adapt it to new conditions ; how a change effected in 

 the circulatory function produces in the vascular system cer- 

 tain anatomical modifications which may be predicted before 

 they take place ; how the senses acquire new qualities by 

 exercise, or lose by desuetude their former powers. These 

 changes of function under the influence of the function itself 

 are accompanied by anatomical modifications in the apparatus, 

 physiologically modified. 



The first demonstration to be furnished will be to ascertain 

 one of these transformations, and to show that it is always 

 produced in a certain manner under certain circumstances. 

 And if, in the second phase of the experiment, it can be 

 proved that hereditary descent transmits even the least part 

 of the modification thus acquired, the development theory will 

 be in possession of a solid starting-point. 



This seems to be the true course to follow, if we desire to 

 obtain a solution of this important question. During several 

 years serious efforts have been made in this direction. Having 

 been ourselves for a long time conversant with the problems 

 of animal mechanism, we have often been induced to refiect 

 on the reciprocal relations of the organs of locomotion and of 

 their functions. We will therefore attempt to show how the 

 skeleton and the muscular apparatus harmonize with the 

 movements of each animal under the ordinary conditions of its 

 existence. 



