VETERINARY ANATOMY INTRODUCTION Anatomy is the branch of biological science which deals with the form and structure of organisms, both animal and vegetal. It is therefore in close correlation with physiology, which treats of the functions of the body. Etymologically the word "anatomy" signifies the cutting apart or disassociat- ing of parts of the body. In the earlier phases of its development anatomy was necessarily a purely descriptive science, based on such observations as were possible with the unaided eye and simple dissecting instruments — the scalpel, forceps, and the like. At this time, therefore, the term adequately expressed the nature of the subject. But as the scope of the science extended and the body of anatomical knowledge grew, subdivisions became necessary and new terms were introduced to designate special fields and methods of work. With the introduction of the mi- croscope and its accessories it became possible to study the finer details of structure and minute organisms hitherto unknown, and this field of inquiry rapidly developed into the science of microscopic anatomy or histology as conventionally distinguished from gross or macroscopic anatomy. In the same way the study of the changes which organisms undergo during their development soon attained sufficient im- portance to be regarded on practical grounds as a separate branch known as embryology. This term is usually limited in its application to the earlier phases of development during which the tissues and organs are formed. The term ontogeny is used to designate the entire development of the individual. The ancestral history or phylogeny of the species is constituted by the evolutionary changes which it has undergone as disclosed by the geological record. Comparative anatomy is the description and comparison of the structure of animals, and forms the basis for their classification. By this means — including extinct forms in the scope of inquiry — it has been possible to show the genetic relationship of various groups of animals and to elucidate the significance of many facts of structure which are otherwise quite obscure. The deductions concerning the general laws of form and structure derived from comparative anatomical studies constitute the science of morphology or philosophical anatomy. The morphologist, however, deals only with such anatomical details as are necessary to form a basis for his generalizations. The anatomical knowledge required in the practice of medicine and surgery is evidently of a different character and must include many details which are of no particular interest to the morphologist. Special anatomy is the description of the structure of a single type or species, e. g., anthropotomy, hippotomy. Veterinary anatomy is the branch which deals with the form and structure of the principal domesticated animals. It is usually pursued with regard to pro- fessional requirements, and is therefore largely descriptive in character. As a matter of convenience the horse is generally selected as the type to be studied in detail and to form a basis for comparison of the more essential differential characters in the other animals. Two chief methods of study- are employed — the systematic and the topo- graphic. In the former the body is regarded as consisting of systems of organs or 2 17
