INTRODUCTORY. 
21 
out into a girdle, or pelvis. In youth, this process is divided 
into three pairs of bones : the ilium, which is attached to the 
spine; the pubis, which forms the anterior of the pelvis; and 
the ichium, which forms the posterior part. At the point of 
union of these bones, there is a cavity into which the thigh is 
articulated, to which is attached the leg, composed of two 
bones, the tibia and fibula. The leg is terminated by the foot, 
composed of parts analogous to those of the hand, and are 
termed the tarsus, metatarsus, and toes. 
The head of the Mammalia is always articulated by two con¬ 
dyles upon the atlas, or first vertebra. 
The cranium is divided into three compartments. The ante¬ 
rior is formed of the two frontal bones and the ethmoid; the 
intermediate, by the parietal bones and the sphenoid; and the 
posterior by the occipital. Between the occipital bones and 
the sphenoid, are inserted the temporal bones, a part of which 
properly belong to the face. 
In the foetus the occipital bone is divided into four parts ; the 
body of the sphenoid into two, and three of its pairs of alee are 
separate. The temporal bone is divided into three, one of 
which serves to complete the cranium, another to close the 
labyrinth of the ear, and the third to form the sides of its cavity. 
These parts of the bones of the cranium unite more or less 
quickly in the different species, and end by perfect union in the 
adult. 
The face is formed by two maxillary bones, between which 
the nasal canal passes; they have the two intermaxillary bones 
in front, and the two palatines behind; between these descends 
the single lamina of the ethmoid bone, called the Vomer. At 
the entrance of the nasal canal, are the bones proper to the 
nose. The jugal, or cheek bone of each side, unites the maxil¬ 
lary bone to the temporal, and often to the frontal bones; and 
finally, the lachrymal occupies the internal angle of the orbit, 
and sometimes a part of the cheek. 
The brain consists of two hemispheres, united by a medul¬ 
lary lamina, called the corpus callosum, contains two ventricles, 
and inclosing four pair of tuberculce, or eminences; these are 
called the corpora striata, or striated bodies, thalami optici, or 
optic beds, nates, and testes. Between the thalami optici is a 
third ventricle, which communicates with a fourth, situated be- 
