B5o ELEMENTS OF MAMMALIAN ANATOMY. 
the peritoneum and pleura; (2) minute thin-walled vessels 
beginning by capillary mouths in the spaces just described 
and leading to larger vessels which empty into the tracheal 
trunks or thoracic duct; (3) the glands, which vary in size 
from a mustard-seed to two centimeters in diameter, arrd 
are located chiefly on the side of the neck, in the axillary 
region, at the bifurcation of the trachea; in the inguinal 
region, lumbar region, and mesentery; (4) the two tracheal 
trunks and thoracic duct (Fig. 80). 
One of the largest of the lymphatic spaces is the greater 
cavity of the peritoneum. The cavity of the lesser perito- 
neum, a large lymphatic space, may be shown by separating 
the layers of the great omentum carefully. The cavity of 
the pleura within the chest is also a large lymphatic space. 
Numerous small lymph spaces are present in all parts of the 
body. The lymphatic capillaries originating in these spaces 
are invisible to the naked eye, but their union into larger 
vessels may be demonstrated satisfactorily in a cat just 
killed, by pulling forward the tongue, and injecting very 
slowly beneath the skin, on its ventral aspect five or ten 
centimeters of a two per cent. solution of Berlin blue in 
warm water. 
The lymph glands (Fig. 80) of the cat are not nearly so 
numerous as in man, The largest lymph gland is the 
pancreas Aselli in the mesentery. It is considerably flat- 
tened and about two centimeters long. A few other very 
small lymphatic glands are also present in the mesentery. 
The two largest lymph glands of the head are just beneath 
the skin craniad of the submaxillary gland. On the side 
of the neck beneath the cephalohumeral muscle are three 
large lymph glands at the cranial border of the scapula. 
A small axillary gland lies on the caudal side of the axillary 
vein beneath the scapula. A single popliteal gland is in the 
popliteal space, an inguinal gland lies on each side of the 
