248 ALBERT KUNTZ 



cells as a fact. The present series of observations shows, moreover 

 that the migration of medullary elements plays a far more im- 

 portant role in the development of the peripheral nervous system 

 than has hitherto been admitted. Direct observations have 

 shown that medullary cells migrate into the ventral roots of the 

 spinal nerves and into the roots of several of the cranial nerves. 

 The present observations have further shown that such cells 

 migrate also into the dorsal roots of the spinal nerves and into 

 the roots of the vagus and the spinal accessory nerves. I have 

 also observed medullary cells migrating into the semilunar gan- 

 glia. Furthermore, it has been shown that some of the cells 

 which migrate peripherally from the neural tube and the cerebro- 

 spinal ganglia give rise to the sympathetic nervous system. 



(b) The neurilemma. — An extended discussion of the develop- 

 ment of the neurilemma is beyond the scope of this paper. Inas- 

 much, however, as the histogenesis of the neurilemma is so inti- 

 mately related to the histogenesis of the sympathetic neurones, 

 its origin may be considered briefly at this point. As the "indiff- 

 ent " cells migrate peripherally from the neural tube and the spinal 

 ganglia, they migrate not only into the anlagen of the sympa- 

 thetic trunks but also along the growing fibers beyond the origin of 

 the communicating rami. These cells as well as the cells which, as 

 has been shown, remain distributed along the nerve-trunks after 

 migration has ceased, obviously take part in the development of 

 the neurilemma. They cannot be accounted for in any other way. 



Not a few of the more recent investigators, including the advo- 

 cates of the theory of local differentiation and the multicellular 

 nature of nerve-fibers, are of the opinion that the neurilemma is of 

 ectodermal origin. We agree with the advocates of local differenti- 

 ation on this point, but we must disagree with them as to the man- 

 ner in which the cells giving rise to the neurilemma arise and are 

 distributed along the nerve-fibers. It is significant that Kolliker 

 ('05), though formerly of the opinion that the neurilemma is of 

 mesodermal origin, came to the conclusion, in his last research, 

 that some of the cells which wander out from the spinal ganglia 

 give rise to the neurilemma of the sensory fibers, and that the neuri- 

 lemma is everywhere of ectodermal origin. Carpenter ('06) has 



