pat hoe C. JUDSON HERRICK 
lobe of mammals, is evidently the correlation of olfactory with 
other exteroceptive impressions belonging to the somatic sen- 
sorysystems.” This conclusion was based chiefly on three ana- 
tomical features of this part of the frog brain: 1) it receives the 
strong dorsolateral olfactory tract; 2) it is broadly connected by 
correlation fibers with the hypothalamus and primordial hippo- 
campus; 3) it receives ascending non-olfactory fibers from the dor- 
sal part of the thalamus. Kappers (Folia Neurobiologica, Bd. 5, 
1911, p. 625) questions the validity of the last point on the ground 
that the mammalian pyriform is not known to receive projection 
fibers from the dorsal thalamus, and if such are present in the frog 
their distribution area should be considered neopallial. No such 
homology as I have suggested can be regarded as exact, for the 
amphibian brain nowhere exhibits a degree of differentiation 
which permits clear-cut definition of regions precisely comparable 
with those of mammals; but the question raises a principle which 
justifies a further inquiry. 
The pyriform lobe of lower mammals is clothed with true cor- 
tex, i.e., superficial gray matter, and rostrally this passes by in- 
sensible gradations into the lateral olfactory nucleus, a part of 
the primordial subcortical olfactory area. Immediately internal 
to this pyriform cortex are the lentiform nucleus and the amyg- 
dala. In lower mammals the lentiform nucleus is related by in- 
numerable fibers (probably mostly descending) with the cerebral 
peduncle, there is a dense neuropil between the lentiform nucleus 
and the pyriform cortex (Cajal, ’11, p. 722, fig. 462), and the 
nucleus is traversed by very numerous radiating fibers connected 
with the pyriform cortex. So intimate, indeed, is the connection 
between the nucleus and the overlying pyriform cortex that Cajal 
(loc. cit., p. 514) says that the lentiform nucleus seems to be a 
dependency of the pyriform cortex. This relation is probably 
reciprocal. 
Now in the frog there is no true cerebral cortex in the lateral 
wall of the hemisphere, but the other structures mentioned are 
related as just described. And ascending thalamic projection 
fibers from the thalamo-frontal tract cross the zona limitans la- 
teralis from the ventrolateral quadrant (primordial striatum) to 
