428 O. LARSELL 



dorsal (vomeronasal) bundle and the main bundle of olfactory 

 fibers proper, as shown in figure 1. At this point it turns to 

 follow these bundles, passing between them in such a manner 

 that it could not be traced further by the method of dissection. 

 Sections, however, reveal the further course of the main bundle 

 of the nerve and indicate the presence of numerous ganglionic 

 cells scattered along its trunk as it passes over the mesial surface 

 of the olfactory bulb. These cells form clusters of various sizes. 

 One of the largest of these clusters is no doubt indicated by the 

 swelUng (fig. 1, gn.') shown in the dissection. Another and larger 

 ganghonic mass is shown (fig. 3, gn.) at the point where the ter- 

 minaUs passes lateral to the vomeronasal bundle. This corre- 

 sponds to the position usually occupied by the largest cluster of 

 cells in the majority of the embryos which were sectioned. 



From the position of this ganglion distally the nerve could not 

 be followed further by the method of dissection, because its 

 strands became too intimately mingled with those of the olfactory 

 and vomeronasal nerves. Fortunately, however, in some of the 

 series of the older stages studied, a differential stain was obtained 

 by the method previously described, so that the terminahs bundles 

 could be distinguished from those of the other two nerves and, 

 further rostrad, from the fibers of the ophthalmic branch of the 

 V nerve. This differentiation was aided by the fact that the 

 olfactory and vomeronasal nerves appear as compact bundles of 

 wavy fibers with few nuclei scattered among them. The strands 

 of the nervus terminalis are smaller and much less compact and 

 present relatively numerous sheath nuclei as well as larger gan- 

 glionic cells. Where the strands of the trigeminus were inter- 

 mingled on the septum, they also had a characteristic appearance, 

 apparently due to the process of myelination, as well as to dif- 

 ferential staining. These characteristics, however, could not be 

 noted with any degree of certainty in the smaller tracts, so that 

 the reconstruction represented in figure 3 indicates only the 

 larger bundles and their grosser ramifications. 



In some of the preparations the nerve was seen to divide in- 

 tracranially at the ganglion gn. into two strands, which, however, 

 reunited to form a compact trunk before the nerve left the brain 



