94 Journal of Comparative Natrology and Psychology. 



In the nervous system of vertebrates networks of cells and 

 fibers have been studied chiefly in connection with the blood 

 vascular system. They have been described by Dogiel ('93, 

 '98), Leontowitsch (:01), Cavalie (:02). Bethe ('95, :03) 

 and others. Bethe states that such networks are present 

 throughout the whole integument of the frog. They form a 

 close network about the blood vessels and a wide-meshed sub- 

 epithelial plexus. Dogiel ('98) and Leontowitsch (:01) have 

 carefully studied the networks in the human skin. They assert 

 that connections exist between these structures and the medul- 

 lated fibers, but their figures do not convince one of this. Their 

 statements have, however, been verified by Bethe (:03) who fig- 

 ures a medullated fiber continuous with a wide-meshed sub-epi- 

 thelial plexus. In the vertebrate heart also, Dogiel ('98), Hof- 

 MANN (:02) and Bethe (:03) have observed independently a net- 

 work of cells and fibers surrounding the muscle bundles. This net- 

 work resembles closely the diffuse nervous system of the Me- 

 dusae and Bethe maintains that the structures he has seen are 

 undoubtedly of a nervous nature. 



It has been stated even recently by certain investigators, 

 that both the cells and fibers composing these networks are non- 

 nervous structures. Bardeen (:03), among others, has ex- 

 expressed his doubts as to their nervous character ; he criticises 

 Leontowitsch and suggests that the whole network described 

 by the latter may be composed entirely of connective tissue. 

 Even if the fibers are nervous structures the cells may be mere- 

 ly sheath cells. 



It is important both to the teacher and student of neurology 

 that these doubts be either confirmed or entirely removed. If 

 networks of true nerve cells and fibers really exist in the integu- 

 ment of vertebrates, then the idea that the peripheral nerves 

 originate only from ganglion cells in or near the central nervous 

 system must be abandoned. If, however, the networks are 

 proved to be nothing more nor less than connective tissue struc- 

 tures, the opponents of the neurone theory have lost one of 

 their strongest arguments. 



My research was begun in the Physiological Institute of 



