THE PACA OF BRAZIL. 
137 
the entrance of the inferior cava. From the longitudinal 
position of tlie heart in the middle of the thorax, with its 
apex directed to the centre of the diaphragm, the inferior 
cava passed upwards about 3 inches, after perforating the 
diaphragm, before it reached the right auricle. The mus- 
cular fasciculi in the right auricle were disposed in regular 
arborescent forms. The tricuspid, mitral and semilunar 
valves, presented nothing peculiar ; but the fleshy columns 
of the right ventricle were more than usually prominent 
and numerous. All the cavities of the heart were distended 
with firm coagula of blood, but no tubercle appeared on 
any part of the organ. The heart had a compressed, ovate 
form, measuring 1 1 inches in its greatest breadth, and 
inches from the base to the apex. Two branches were 
given off from the arch of the aorta, as in other quadru- 
peds. The pericardium was thicker and stronger than we 
generally find it in Rodentia. The phrenic nerves, and the 
nerves generally, of this animal were large and distinct. 
The Paca is stated by Lacepede to possess a remarkable 
sensibility, and its surface is covered only with a loose 
bristly hair, like that of a hog. 
The great length of the intestinal canal, and the size of 
the stomach and coecum, point out more distinctly than 
the chisel-shaped fore teeth, the kind of food on which this 
animal naturally subsists. The specimen I examined was 
fed, during its confinement, on potatoes boiled or unboiled, 
loaf-bread, apples, cabbage, or almost any kind of vege- 
tables. In their natural state, these animals live on herbs, 
or shrubs, or dig up from the ground with their very long 
claws succulent roots, as we observe done by the common 
hog. The Paca resembles the hog in the great size of the 
back part of the abdomen, and in the grvmting sound it 
frequently produces. The oesophagus entered near the 
middle of the upper margin of the stomach, leaving a por- 
