THE AMYGDALA IN AMPHIBIA 219 
these sections, though their fibers are unmyelinated. These 
are sketched in on the left side of the drawings, their terminal 
relations (which are not demonstrated by the Weigert sections) 
being added from data derived from, Golgi sections in various 
planes. 
These connections are also shown as seen in horizontal sections 
by the Golgi method of the cricket frog, Acris gryllus, in figures 
p. hip. 
lob. p. LE Ol. G45 
z. lim. med. 7 ey vl. 
tr ol.vl. i! a a2: Sptr od f 
m.C. 
g.c. 
septum 
xxxi- 197 
Figs. 1 to12 Aseries of transverse sections through the brain of Rana 
pipiens. X12. The outlines and arrangement of cells and myelinated fibers are 
drawn to scale from a series of Weigert sections. The sections are somewhat 
compressed dorsoventrally and are slightly oblique, the right side being farther 
rostral than the left. The arrangement of cells is necessarily somewhat conven- 
tionalized on:account of the small scale of the drawings. 
These sections were prepared by the Weigert method, fixing in formalin and 
potassium bichromate, mordanting the sections in copper acetate, and destaining 
in potassium permanganate and the oxalic potassium sulphite mixture. The 
destaining was arrested at a point which differentiated the myelinated fibers, 
but left considerable brownish-yellow color in the background. All cell bodies 
are clearly visible and their arrangement was further controlled by comparison 
with sections stained with toluidin blue. Some of the unmyelinated tracts are 
also differentiated by the ‘brown reaction.’ 
The myelinated fibers are entered only on the right side of the drawings. 
On the left side are entered the ventrolateral olfactory tract and the dorsal 
olfactory projection tract, both of which are unmyelinated. The courses of 
these tracts can be followed in the Weigert sections throughout their length 
except near their ends, but the details of these unmyelinated fibers are drawn 
in by comparison with various other series of transverse and longitudinal sections 
prepared by the methods of Golgi and Cajal. 
Fig. 1 On the left the section passes through the extreme caudal end of the 
vomeronasal formation, showing its layers of granule cells and mitral cells. 
There are no glomeruli at this level; on the right these are present. The un- 
myelinated fibers of the ventrolateral olfactory tract have assembled from the 
vomeronasal formation to form a compact bundle in the deeper part of the zona 
limitans lateralis. 
