154 JOURNAL OF COMPARATIVE NEUROLOGY. 
the preceding one by its associative or commissural value, and 
it is also readily recognizable by its smaller size (Fig. 40). The 
cell-body tends to retaina globular form. It gives origin to 
two or three dendrites which radiate from it at equidistant 
points. The dendrites are only moderately stout, and they are 
never of great length. They branch buta few times. Their 
surface is sparsely studded with small gemmules. The axone 
may terminate on the same side of the brain; or it may enter 
the pallial commissure, (Fig. 31, . c.), for decussation, termin- 
ating in the opposite half. The neurone shown in Fig. 40 is an 
example of the commissural class. 
The internal structure of a neurone of either the associa- 
tive or the commissural type is drawn in Fig. 68, as. x. The 
nucleus is a subspherical mass, so large that it occupies prac- 
tically the whole of the cell-body. The only cytoplasm dis- 
tinguishable is that which composes the bases of the dendrites. 
The nucleus stains quite deeply, owing to the dense reticulum 
of chromatin which pervades it. The cytoplasm has only a few 
tigroids of small size, an evidence of a feeble degree of activity 
for this type of neurone. 
c. Cajal Neurones.—Still a third type of neurone is clearly 
the representative of the Cajal cell which Ramon y Cajat (’91) 
described from the cerebral cortex of the rabbit, and which 
Retzius (93), and Veratrti (’97) have designated after the 
name of the discoverer. CAJAL neurones have been observed 
in all of the higher vertebrates by various investigators, and 
their identification in the brain of Mustelus makes it probable 
that they are common to all groups. 
A CajaL neurone is drawn in Fig. 41. This neurone occu- 
pies a superficial position, just beneath the stratum of fibres 
noted above; refer to Fig. 31. The cell-body is an irregularly 
elongated oval, with its major axis horizontal. From its oppo- 
site extremities, thick dendrites arise which run more or less 
nearly parallel with the limitans externa. A dendrite does not 
have marked turns in its course. It gives off branches along 
its upper margin which ascend toward the surface of the brain, 
while a few branches are derived from its under side and pene- 
