COMPARATIVE ANATOMY is the term employed to express that branch of anatomy in which the construction, form, and structure of two or more animals are compared with each other, so as to bring out their features of similarity or dissimilarity. It is sometimes used, in contrast with the term human anatomy, to signify the anatomy of the lower animals, but this is an imperfect and inexact use of the term, as the anatomy of man may be made comparative when it is examined in comparison with that of animals. The study of comparative anatomy is of especial importance to the physiologist, the embryologist, the veterinarian, and the zoologist. To the physiologist because, from the comparison of the bodies of different animals with each other, modifications in the size, form, and structure of any particular organ can be traced, and conclusions can be drawn on the importance of the function of the organ in the economy. Moreover, with a knowledge of comparative anatomy, the physiologist can conduct experiments on animals which have organs similar in structure to those of man, and determine their function more precisely than would be possible in the human body. To the veterinarian a knowledge of the comparative anatomy of the domestic animals is essential to the study of their diseases. To the embryologist, a knowledge of the anatomy of different animals throw’s light on the signification of the structural changes which the body of any particular animal passes through in the course of its development. To the zoologist, a knowledge not only of the external form but of the internal structure of animals is essential in order that he may frame a precise system of classification. In the present work the anatomy of the different great classes and some of the more important orders of the ...