Herrick, Bfain of Certain Reptiles. 1 23 



uncles. The tract there breaks up but part of it may be traced 

 caudo-mesad to the hippocampal lobe. This tract for some 

 time evaded us because it is not superficial but lies near the 

 ventricle. There seem to be two main branches in the pero, 

 one arising from the dorsal and the other from the ventral as- 

 pects, both curving to a common point on the lateral aspect. 



It may perhaps be doubted whether this single strong band 

 represents the precommissural radix or the radix lateralis, or 

 both. Some fibres from it do, in fact, seem to enter the pre- 

 commissure but, if our observation is correct, a larger part pass- 

 es to the hippocampal region, (Plate XVI, Fig. 9.) There is a 

 smaller tract passing from the region of the precommissure ceph- 

 alad, which may correspond to the olfactory branch of the com- 

 missure but, inasmuch as the radix obviously branches about 

 half-way from the ruber to the commissure and one portion 

 passes dorso-mesad to the hippocampal region, it is better to 

 think of the two radices as fused until more definite evidence is 

 at hand. The region where the compound radix enters the cere- 

 brum is differentiated from the adjoining cortex by the presence 

 of certain deeply staining cells whose axes lie in the plane of 

 transverse section, while the remaining cells are less susceptible 

 to stain, less shrunken and with clear granular nuclei. Whether 

 the peculiar dark cells which are locally distributed in the cortex 

 should be regarded as motor or simply such cells as for any rea- 

 son have been recently active, is yet a question. There is, of 

 course, a possibility that the difference is wholly accidental, but 

 this seems improbable. Fig. 12, Plate XVI, illustrated a por- 

 tion of the transverse section with the olfactory radix. At a 

 point farther caudad the course of the above olfactory tract is in- 

 terupted by nuclei in the course of the fibres. These are evidently 

 the second neurons in the course of the tract if the fibres to 

 this point are supposed to be derived from the specific olfactory 

 ganglia. 



In longitudinal sections it is seen that the region where the 

 disperse olfactory fibres converge to form the radix is at a point 

 near the peculiar lateral olfactory lobule which lies adjacent to 

 the post-rhinal lobe or ventral tuberosity of the cerebrum. (Fig. 



