Comparative anatomy of vertebrates

Preface

Vertebrate anatomy is everywhere taught by the laboratory method. The student studies and dissects representatives of several classes, thus gaining an autoptic knowledge of the various organs and their positions in these forms. These facts do not constitute a science ’Until they are properly compared and correlated with each other and with the conditions in other animals. • It is the purpose of the author to present a volume of moderate size which may serve as a framework around which these facts can be grouped so. that their bearings may be readily recognized and a broad conception of vertebrate structure may be obtained.

' In order that this may be realized, embryology is made the basis, the various structures being traced from the undifferentiated egg into the adult condition. This renders it easy to compare the embryonic stages of the higher vertebrates with the adults of the lower and to recognize the resemblances and differences between organs in the separate classes. There has been no attempt to describe the structure of any species in detail, but rather to outline the general morphology of all vertebrates. To aid in the discrimination of the broader features and the more minor details, two sizes of type have been used, the larger for matter to be mastered by the student, the smaller for details and modifications in the separate classes to which reference may need to be made.

Considerable space has been given to the skull, as there is no feature of vertebrate anatomy which lends itself more readily to comparative study of the greatest value to the beginning student, while the same specimens can be used in the laboratory year after year. The skull also has a special interest since nowhere else is there the same chance of tracing modifications in all groups since the first appearance of vertebrates on the earth. To aid in this, extinct as well as recent species have been included.

It was the desire of the author to adopt the nomenclature of the German Anatomical Society (‘BNA’), but this was often found impracticable. The BNA was based solely upon human anatomy and it fails utterly in many respects when the attempt is made to transfer its terms to other groups. The single example of ‘transverse process’

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is sufficient to illustrate this. To the writer another objection is that the BNA strives to do away with all personal names. These, it would seem, have a great value as they are indications of the history of anatomical discovery and memorials of the great anatomists of the past. Dorsal and ventral are used instead of the anterior and posterior of human anatomy, while anterior indicates toward the head, posterior toward the tail, these terms being readily applied to all vertebrates, man only excepted. Cephalad and caudad, adopted by some, lead to occasional peculiar phrases. The German word ‘anlage’ has been adopted bodily, and seems to call for no defense. It implies the indifferent embryonic material from which a part or an organ develops.

The illustrations have been drawn or redrawn expressly for this work. Some of them are original, some based on figures in special papers. Practically none have ever appeared in any text-book in the English language. In selecting the objects to be figured especial pains has been taken to avoid the forms usually studied in our laboratories, thus relieving the student of the temptation of copying the figure, instead of drawing from nature. Especial thanks are due to Professor C. F. W. McClure, who allowed me to draw at will from the splendid collection which he has built up at Princeton. I hese figures are indicated by the word ‘Princeton’ followed by the number of the preparation in the museum of the University.

Tufts College, Mass.

Contents

Introductory embryology

Epithelial tissues

Nervous tissues