Part 2

THE UROGENITAL SYSTEM URINARY ORGANS OF THE HORSE 469 The Kidneys 469 The Ureters 475 The Urinary Bladder 475 THE ADRENAL BODIES 477 URINARY ORGANS OF THE OX 478 URINARY ORGANS OF THE PIG 481 URINARY ORGANS OF THE DOG 483

THE MALE GENITAL ORGANS MALE GENITAL ORGANS OF THE HORSE 485 The Testicles 485 The Scrotum 487 The Vas Deferens 488 The Spermatic Cord 489 The Tunica Vaginalis 489 Descent of the Testicles 490 The Vesiculæ Seminales 491 The Prostate 493 The Uterus Masculinus 493 The Bulbo-urethral Glands 493 The Penis 494 The Prepuce 496 MALE GENITAL ORGANS OF THE OX 500 MALE GENITAL ORGANS OF THE PIG 504 MALE GENITAL ORGANS OF THE DOG 506

THE FEMALE GENITAL ORGANS GENITAL ORGANS OF THE MARE 508 The Ovaries 508 The Uterine or Fallopian Tubes 511 The Uterus 511 The Vagina 514 The Vulva 514 The Urethra 515 The Mammary Glands 516 GENITAL ORGANS OF THE COW 517 GENITAL ORGANS OF THE SOW 521 GENITAL ORGANS OF THE BITCH 522

ANGIOLOGY THE ORGANS OF CIRCULATION 524 BLOOD-VASCULAR SYSTEM OF THE HORSE 525 The Pericardium 525 The Heart 526 The Pulmonary Artery 535 The Systemic Arteries 535 The Coronary Arteries 537 The Brachiocephalic Trunk or Anterior Aorta 537 Arteries of the Thoracic Limb 556 Branches of the Thoracic Aorta 565 Branches of the Abdominal Aorta 566 Arteries of the Pelvic Limb 578 The Veins 585 The Pulmonary Veins 585 The Systemic Veins 585 The Anterior Vena Cava and its Tributaries 586 The Posterior Vena Cava and its Tributaries 595 THE LYMPHATIC SYSTEM 599 Lymphatic System of the Horse 600 The Lymph Glands and Vessels of the Head and Neck 601 The Lymph Glands and Vessels of the Thorax 603 The Lymph Glands and Vessels of the Abdomen and Pelvis 604 The Lymph Glands and Vessels of the Thoracic Limb 605 The Lymph Glands and Vessels of the Pelvic Limb 606 THE FŒTAL CIRCULATION 606 BLOOD-VASCULAR SYSTEM OF THE OX 608 The Pericardium and Heart 608 The Arteries 609 The Veins 621 LYMPHATIC SYSTEM OF THE OX 623 CIRCULATORY SYSTEM OF THE PIG 626 The Pericardium and Heart 626 The Arteries 627 The Veins 630 Lymphatic System of the Pig 630 CIRCULATORY SYSTEM OF THE DOG 632 The Pericardium and Heart 632 The Arteries 633 The Veins 641 Lymphatic System of the Dog 643

NEUROLOGY—THE NERVOUS SYSTEM GENERAL CONSIDERATIONS 644 NERVOUS SYSTEM OF THE HORSE 648 The Spinal Cord 648 The Brain 652 The Cranial Nerves 676 The Spinal Nerves 692 SYMPATHETIC NERVOUS SYSTEM OF THE HORSE 710 NERVOUS SYSTEM OF THE OX 715 NERVOUS SYSTEM OF THE PIG 720 NERVOUS SYSTEM OF THE DOG 724

ÆSTHESIOLOGY THE SENSE ORGANS AND SKIN OF THE HORSE 734 The Eye 734 The Ear 747 The Skin 761 The Olfactory and Gustatory Apparatus 772 THE SENSE ORGANS AND SKIN OF THE OX 772 THE SENSE ORGANS AND INTEGUMENT OF THE PIG 777 THE SENSE ORGANS AND INTEGUMENT OF THE DOG 779

INDEX 783

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 disassociating 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 microscope 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 importance 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 professional 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 =topographic=. In the former the body is regarded as consisting of systems of organs or apparatus which are similar in origin and structure and are associated in the performance of certain functions. The divisions of =systematic anatomy= are:

1. Osteology

2. Arthrology

3. Myology

4. Splanchnology

(1) Digestive System

(2) Respiratory System

(3) Urogenital System

(a) Urinary Organs

(b) Genital Organs

5. Angiology

6. Neurology

7. Æsthesiology