NERVUS TERMINALIS: MAMMALS 



25 



portion of the plexus figured. This nerve shows development of 

 the myehn sheaths, while the intracranial portion of the nervus 

 terminalis of this specimen (fig. 23) gave no indication of myelin 

 sheaths as brought out by the Weigert treatment. It does not 

 seem likely that such sheaths would be formed in the peripheral 

 portion of the nerve at an earlier date than they are formed in 

 the part of the nerve nearer the brain. It is therefore assumed 

 that they are fibers belonging to the already myelinated anterior 

 ethmoidal nerve. 



So far as this material indicates, the central roots of the ter- 

 minalis, which are easily followed in the sections to their points 



per: 



Fig. 6 Two bipolar cells and some of the nerve fibers from periphery of main 

 ganglion (fig. 3, gn.) of the nervus terminalis in kitten of two weeks. Pyridin- 

 silver technique. X 1266. 



of entrg.nce into the brain, are composed entirely of unmyelinated 

 fibers. In kittens of two weeks, myelinated fibers are found in 

 the intracranial plexus, although in these also no clear evidence 

 of such fibers was found among the strands which enter the 

 brain. 



To avoid as far as possible the entrance of fibers from the 

 fifth nerve as a factor, the greater part of the histological studies 

 to be described was confined to the intracranial plexus and 

 ganglia of the terminalis. 



Histological. The plexiform character of the nerve in the cat, 

 together with the structure of the ganglion cells to be described 



