200 Kelation of Nervous System to the Developing Musculature 



by direct experimentation, Imt in devising experiments for this purpose 

 it is necessary to formulate clearly just what is to be determined, for it 

 is obvious from the facts already referred to, that the nervous system 

 may possibly exert its influence in a variety of ways. 



The first questions which I had in mind in beginning the present in- 

 vestigation were the comparatively simple ones whether a stimulus from 

 the nervous system is necessary in order to start the differentiation of 

 striated muscle fibers and whether the musculature is dependent upon the 

 nervous system in its further development, including the grouping of the 

 fibers into individual muscles. It is the first question that has of late 

 been most freely discussed and has been answered affirmatively by Neu- 

 mann and Herbst ; even Eubin emphasizes the fact that of all the tissues 

 in the regenerating limb the voluntary muscle is the most dependent 

 upon the integrity of the nerves. While on the other hand Schaper's 

 experiments do show that the central nervous system has no general 

 directive action upon the development of the frog, they do not answer 

 the first question just stated, for Sehaper removed only the brain, leaving 

 the spinal cord intact; and besides, embryos 6 mm. long with well- 

 developed tail were used; in such embryos the motor nerve roots have 

 already established connection with the muscle plates and the differen- 

 tiation of the contractile substance is begun. The musculature at the 

 time of experimentation in Schaper's experiments would thus fall into 

 the second period of Neumann. To test this question it is necessary to 

 remove the spinal cord at a period of development, before there are traces 

 of peripheral nerve fibers or contractile substance in the musculature. A 

 series of experiments of this kind is described below in the first section. 



Another question which may to advantage be considered in connection 

 with that of the formative influence of the -nervous system, is whether the 

 normal processes of ontogeny are regulated by functional stimuli, or 

 to state a more particular phase of the jiroblem, whether the normal 

 exercis^ of function is a necessary factor in determining the early course 

 of development of the musculature. While the first series of experi- 

 ments may be used in this connection, the necessary mutilation of the 

 embryo enters as a disturbing factor. This question may be best tested 

 experimentally by causing the suspension of muscular function in devel- 

 oping embryos through the action of a drug. Acetone chloroform is ex- 

 ceedingly well adapted to this purpose. In the second section of the 

 present paper the results of rearing embryos in solutions of this substance 

 are given. 



