WOBK OF THE PHYSIOLOGICAL STATION AT PARIS. 411 



Now, except in certain rare cases, the effects of the mutilation of peri- 

 pheral organs are not transmitted to the oftspring. Bnt it is not the same 

 with lesions that affect the uervons system. This fact has been well 

 established by the experiments of Brown-Sequard. In guinea pigs 

 this eminent physioh)gist saw cnrions deformations of the limbs and 

 exophthalmia produced as a consequence of nervous lesions; and these 

 modifications may be transmitted hereditarily throughout a long series 

 of generations. It seems that in such cases the traumatism has affected 

 fnnction at its very origin; that is to say, in the organ placed at the 

 head of the physiological hierarchy. 



There is, indeed, an evident subordination among the different parts 

 of the organism; the nervous system conceives acts and directs them 

 to be carried out; the muscles perform these acts; the bones and the 

 articulations bear the strains. May we not suppose that some ncAv 

 exterior circumstances excite in an unaccustomed manner the nervous 

 system of an animal so that new conditions bring about new acts and 

 consequently lead to a modification of organs? The modifications thus 

 produced would be transmissible by heredity as in the experiments of 

 Brown-Seqnard. We might thus explain the transformation of animals 

 during the lapse of ages: The variations of the environment create 

 new needs and excite to new acts, affecting first the nervous system, 

 which gradually modifies the organs subordinate to it. 



Thus in the course of the past two centuries the breed of race horses 

 has diverged markedly from its primitive form. The excitation to 

 more rapid and more energetic muscular action is the cause of the 

 modifications revealed by comparative anatomy, which are in great 

 l^art hereditarily transmitted. 



Jonathan Franklin states that kangaroos bred in captivity, having 

 no longer as in their natural habitat to bound over the tall grass, begin 

 to use their fore limbs for walking and running, while they lose in part 

 the robust character of their tails and the power of their hind legs. 

 M. Tegetmeier' states that rabbits, although imported into Australia in 

 quite recent times, have already shown notable modifications, and have 

 acquired by climbing trees habits which they did not have in the country 

 of their origin. These facts and other similar ones should be rigor- 

 ously investigated. The physiological and anatomical modifications of 

 all such cases should be determined with precision, so as to ascertain 

 if they correspond. If these modifications are real and their heredi- 

 tary transmission is well established the theory of evolution will be 

 experimentally demonstrated. 



You see how many questions present themselves and how vast is the 

 experimental field in which the Physiological Station may be used. I 

 hope that I may have inspired you with a desire to seek a solution to 

 all these problems. The task is long and difficult, but it is not beyond 

 the scope of the exi)erimental methods at our disposal. 



In Laud aud Water, Loudou, 1892. 



