THE AMYGDALA IN AMPHIBIA 215 
including Siren, Cryptobranchus, Amphiuma, larvae of lungless salaman- 
ders, and the adult stage of higher amphibians. In these forms, 
ingoing and outgoing currents bear odorous matter to the olfactory 
organ, which is accordingly used to test both the external medium 
and the contents of the oral cavity. This condition, which is common 
to all higher vertebrates, may be called diosmesis. 
In (adult)! single smellers (Necturus)! Jacobson’s organ is wanting 
and the olfactory organ has a very simple condition. In double smellers 
the olfactory organ is complex and Jacobson’s organ is present. 
For the development of a complex olfactory organ, with an organ 
of Jacobson, the nature of the olfactory medium is of less importance 
than the question whether the animal is a single or a double smeller. 
The more recent observations of Broman (’20) on reptiles and 
mammals are commented upon on page 265. 
in the frog the vomeronasal formation (bulbulus olfactorius 
accessorius of Gaupp, 799, p. 99) forms a distinct accessory 
bulb. on the lateral surface of the cerebral hemisphere farther 
caudad than the olfactory formation. Its relations to the 
vomeronasal nerve and organ have been fully described by 
McCotter (17). 
In 1910 in connection with a brief review of the forebrain of 
the frog I described a tract of unmyelinated fibers, the ventro- 
lateral olfactory tract (’10, pp. 422, 444 and figs. 40, 41), which 
passes from the accessory olfactory bulb to the so-called corpus 
striatum, or lateral basal nucleus of the hemisphere. In view of 
the peripheral relationship of the accessory olfactory bulb to the 
vomeronasal organ, it is clear that the ventrolateral olfactory 
tract can be nothing other than the central-conduction pathway 
of the vomeronasal system, and the terminal nucleus of this tract, 
a part of the so-called corpus striatum of the frog, is similarly 
related to the vomeronasal apparatus. 
The fiber connections of the region hitherto called corpus 
striatum in the frog show that it must be separated into two 
clearly distinct parts: 1) a true corpus striatum (paleostria- 
tum) which is very simply developed in the frog, and, 2) farther 
caudad a definite nucleus which is comparable with a part of the 
mammalian nucleus amygdalae. The latter nucleus receives 
1 The words in parenthesis are added with a pen in the copy of the author’s 
reprint sent to me, 
