le le Opler b 
ON THE 
Meee Alas Ol OFTTO. 
BY A. M. BRAYTON. 
The Mammals are air-breathing, warm-blooded vertebrates, having the 
skin more or less covered with hair; respiration never by branchia, but 
after birth by lungs; heart and lungs in the thorax, separated from the 
abdominal viscera by a muscular diaphragm; the blood with red non- 
nucleated blood-corpuscles; biood undergoing a complete circulation, 
being received and transmitted by the right half of the quadrilocular 
heart to the lungs for aeration, and afterward returned by its other half 
through the system; aorta single and reflected over the left bronchus. 
The cerebral hemispheres are connected by an anterior commissure, 
and a transverse superior commissure, the corpus callosum, the latter more 
or less roofing in the lateral ventricles; skull with two occipital con- 
Gyles, one each side of the foramen magnum; lower jaw composed of a 
pair of simple rami, and articulated directly by convex condyles with 
the squamosal bones. Viviparous; foetus developed from a minute egg, 
and provided with an amnion and allantois; young nourished for a time 
after birth by milk secreted in the mammary glands of the mother. 
