82 BULLETIN OF THE LABORATORIES 



is a layer of ganglion cells. These cells are pyramidal and give off 

 three or more acute projections peripherally, but extend into a thick 

 axillary process below. The number of ganglion cells is relatively very 

 small. The bases of these ganglion cells are immersed in a dense zone 

 of neuroglia nuclei, which are oval and furnished with very prominent 

 nucleoli, one always being central, they are not more than one-fifth 

 the length of the ganglion cells, and their function may be to nourish 

 the ganglion cells and insulating layer of the centripital nervous pro- 

 cesses. The following layer is composed of nerve fibres, which are 

 collected in bundles closely invested by nuclei similar to those above 

 described and divided into upper and lower tracts by the olfactory 

 ventricle. The dorsal part of the crus olfactorius has a cortical layer, 

 differing materially from that of adjacent parts of the cerebrum. 



The course of the fibres is difficult to trace in detail. There are 

 two distinct tracts, the upper passing directly to a point below ventral 

 point of the lateral ventricle, partly mingling with the cortical fibres 

 of that region and passing through the base of the corpus striatum, but 

 giving off a branch which unites with the lower superficial tract which 

 passes oblicpiely backward upon the surface to what has been called 

 the pyriform lobe. 



Fig. 9, Plate I. Transverse section of olfactory lobe. (a,) gran- 

 ular layer, (b,) gelatinous layer, (c,) position of ventricle, (d,) gang- 

 lion layer, (g,) glomerular layer, (f,) fibre tracts. 



Fig. I, Plate II. Longitudinal section of anterior part of hemi- 

 sphere and olfactory lobe. Fig. la, fibre bundle, enlarged. Fig. 3, 

 Plate II, section through ganglion and adjacent layers, much enlarged. 

 Fig. 2, Plate II, portion of cortex at base of crus olfactorius. 



[Note.] — Although most of the time devoted to this paper has 

 been employed in the study of the histology, especially of the cortex, 

 his section must be omitted till the next issue, because of vexatious 

 delays. 



