216 Eelation of Xervous System to the Developing Musculature 



influence upon the development of the organism as a whole, the present 

 experiments demonstrate that the nerve elements normally innervating a 

 muscle play no part in its morphogenesis. 



This experimental demonstration of the independence of the develop- 

 ing muscular tissue may be regarded as crucial evidence against the 

 general correctness of the view held by Keumann, oi and 03, that the 

 first development of the muscles takes place under the influence of the 

 nervous system through the agency of the motor nerves. Herbst's, 01, 

 assumption of a formative stimulus proceeding through the sensory 

 nerves is also shown to be erroneous. Of course there is the possibility 

 to be considered that the conditions obtaining in mammals differ, in 

 regard to the action of the nervous system, from those in the frog; but 

 this is not likely, and in view of the relative activity of the developing 

 tadpole, as compared with the mammalian foetus, any differences between 

 the two would most likely be in favor of a more important influence being 

 exerted by the nervous system in the former than in the latter. 



The second series of experiments is like the first in that the effect of 

 possible functional stimuli is entirely eliminated, although the possi- 

 bility still remains that special formative or trophic stimuli, if such 

 exist, are not interrupted by the action of the acetone-chloroform. While, 

 therefore, the latter experiments are in themselves not so conclusive as 

 the former in proving that the histological differentiation of the muscu- 

 lature is independent of the action of the nervous system, the similar 

 results in the two series would indicate that the two methods of elmina- 

 tion of nervous action, the operative and the chemical, are as a matter 

 of fact equivalent. The experiments with acetone-chloroform have the 

 additional value that the function of the nervous system may be restored 

 by the removal of the drug from the organism. In this way the func- 

 tional power of the complex nervous and muscular mechanisms, which 

 carry out the movements of swimming and respiration, may be tested. 

 The surprisingly quick recovery — or better, since the musculature had 

 never shown any activity — the quick acquisition of the power to carry 

 out these movements, shows that the mechanisms in question develop in 

 perfect order, without the influence of normal function in each succes- 

 sive stage. The organism in which this takes place is one which is nor- 

 mally very active, and one in which the power of locomotion is only 

 gradually acquired. While the above fact cannot but strike one as remark- 

 able, it is, nevertheless, on the other hand, in accordance with what 

 should in reality be expected, for such complex mechanisms as, for ex- 

 ample that used in respiration, develop in the mammallian embryo dur- 

 ing intrauterine life without ever havinsr been brought into action. 



