198 Relation of Nervous System to the Developing Musculature 



are destroyed, although later the absence of nervous influences, or perhaps 

 the lacking function, tends to retard the processes and ultimately brings 

 them to a standstill. Woltf, 02, has made somewhat similar experiments 

 upon the axolotl, and concludes that the nervous system does exercise 

 a morphogenetic function in the regeneration of the limbs. 



The data are more meagre concerning the nervous regulati(Mi of purely 

 ontogenetic processes. Loeb, 96, was the first to study this question ex- 

 perimentally; he showed that tlie metamorphosis takes place simultane- 

 ously in the posterior and anterior portions of the amblystoma larva even 

 after the spinal cord has been severed. Later it was shown liy Schaper, 

 98, that the frog embryo develpps normally after the removal of the entire 

 brain. 



A considerable mass of evidence having a bearing upon this question, 

 has been collected from the study of acephalic and amyelic monsters. 

 This evidence is, however, conflicting and the same facts have not always 

 been interpreted in like manner by all investigators. Leonowa, 93, and 

 Fraser, 95, have on the one hand described human fretus in which brain 

 and spinal cord were totally lacking, while the perij^heral sensory nerves 

 and the musculature were normally developed. On the other hand, E. H. 

 Weber, 51, Neumann, 01, and others have described cases in which 

 absence of certain portions of the central nervous system has Ijeen accom- 

 panied liy total absence of musculature in the region normally supplied 

 by the lacking nerves, although skeleton, blood vessels and even tendons 

 were normally developed. 



The discussion has centered especially around the question of the domi- 

 nance of the diiferentiation of the voluntary musculature by the nervous 

 system. Neumann, 01, has given a critical resume of the facts bearing 

 upon this question. He concludes that in cases similar to those described 

 by Leonowa and Fraser, where there is a well-developed muscular system 

 in spite of the total absence of the brain and cord, the nervous system 

 must have developed in the early stages of embryonic life up to a certain 

 point, and that it did not undergo degeneration until after the differentia- 

 tion of the muscular system had taken place. Thus in his effort to 

 harmonize the seemingly conflicting observations referred to above, Neu- 

 mann " reaches the conclusion that the physiological relations between 

 muscle and nerve change during the course of the development of the 

 individual as follows : 



1. The first development of the muscles takes place under the influence 

 of the nervons system and through the agency of the motor nerves, which 



' Op. cit., p. 463. 



