The diseases of the genital organs of domestic animals

Front matter

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Preface

No attempt has been made heretofore to describe systematically the genital diseases of domestic animals. The pathologic processes acting within the genital organs and interfering with the ideal production of young are chiefly hidden from view. Only certain phenomena caused by them become apparent. Of these the most striking phenomenon is the observed expulsion of a fetal cadaver, which is designated abortion. The observer is generally forewarned of impending death of a born animal because it is commonly preceded by visible injury or illness, but abortion produces a profound impression because the death of a potentially valuable unborn animal has occurred unseen and is revealed only when the cadaver is seen to be expelled. This tends to draw a veil of mystery about the event. If the spermatozoon, unfertilized or fertilized ovum, or the small embryo perishes, the dead cell or body is not observed and therefore excites little or no comment.

In the early history of medicine, certain striking phenomena were regarded and described as diseases. When the science of pathology became established, a rearrangement of medical literature became necessary and the phenomena became grouped about their causes, so far as known. It followed that various phenomena which had been regarded as distinct diseases were in some cases due to a common cause. In other cases a phenomenon classed as a disease has been split up because the phenomenon was inconstant in its cause. In primitive veterinary literature glanders and farcy were described as distinct affections, but later it became known that the two supposed diseases were merely separate phenomena resulting from one cause. Nasal gleet occupied a prominent place in primitive veterinary literature, but as veterinary science advanced the phenomenon of nasal discharge was split up, assigned in each case to the disease of which it constituted one symptom, and nasal gleet disappeared from the pages of veterinary literature.

iv Preface

The pathologic processes occurring in the genitalia of animals have been almost wholly described under the primitive method, each striking "phenomenon being elevated to the dignity of a disease. Consequently a certain infection, by causing a wide variety of outstanding phenomena, injected into veterinary literature numerous alleged "diseases" each due to a single infection. It was unavoidable also that a given phenomenon, such as fetal death, which may be due to numerous different infecting agents, should be known as one disease. Thus abortion, metritis, retained fetal membranes, epididymitis, semino-vesiculitis, and dysentery of the new-born, all of which in a given series of cases may be due to an identical infection, have been described as six distinct diseases and scattered from end to end of veterinary literature.

The re-casting of the genital diseases of animals into a systematic treatise is a formidable task, the first effort at which must be very imperfect. In 1909 I published "Veterinary Obstetrics; Including the Diseases of Breeding Animals and of the New Born", in which many of the diseases of the genital organs were included under the primitive plan. It was abandoned at the exhaustion of the first edition. In 1917 I published "Veterinary Obstetrics" and began the preparation of the present volume. The two treatises have been designated "companion volumes" because they are closely allied in subject matter and may be profitably studied together.

The present treatise appears at a critical period in the history of the diseases of the genital organs of animals, when an old, firmly entrenched belief is slowly crumbling and a modern one is struggling for recognition. Abortion has long been regarded as a specific infectious disease, due in a given species of animals to one bacterium and to one only. If an exception arose and a given abortion or group of abortions was apparently due to an infection other than that specified for the species of animal concerned, it was not infectious abortion but merely abortion due to infection.

The belief in a specific irifectious abortion has occupied

Preface v

the central position in the literature upon genital diseases in animals so long, that anyone attempting to write a systematic treatise in this field must either make infectious abortion the cornerstone or reject it wholly. While in this treatise it is held that all abortions in animals (except those induced surgically) are due to infection, it is denied that such infection is specific, as that term is commonly understood in medicine. It is denied as a principle in pathology that conception, parturition, birth, or other physiologic act draws across the path of life an impenetrable barrier to disease. It is held that any infection competent to invade a female may likewise invade a male ; if able to invade a pregnant animal, it may also invade the same animal when non-pregnant ; if it can gain a habitat in the pregnant female, it may persist after parturition ; if it can invade and imperil the life of an embryo or fetus, it may continue through birth and affect the new-born, or may attack the new-born from external sources. Any infection which can invade and injure or kill a post-natal animal, may cause the same injury to it while intra-uterine, provided that contact is made. If tuberculosis or syphilis exists in the pregnant uterus, the infection may invade the embryo. There is no evidence to show, and no reason to believe, that any acute infection may not attack and destroy the embryo if the virus is brought into contact with it. It is true that acute infections, when attacking a pregnant female, rarely if ever pass the intact placental filter and reach the embryo. It does not follow that the embryo is immune to the infection, but merely that it is in a hermetically sealed sac, so isolated that the virus fails to acquire contact.

Although the placental isolation of the embryo is efficient against filterable viruses, the supporters of the "specific infectious abortion" theory hold that certain comparatively large bacteria defy this important law, invade the pregnant female, pass directly to the existing embryo, and cause its death and expulsion. But in invading the pregnant female, presumably through the mouth, the infection is alleged to reach the endometrium and embryo without leaving behind vi Preface

any lesion in its path or causing any disease or sign of disease.

This treatise is built upon the belief that abortion is only an incident in the ravages of infections existing within the pregnant uterus at the date of conception, or deposited with the semen at coitus. The infection is not specific, is not limited to one species of bacterium, invades organs other than the uterus, and involves both sexes and all ages. This general infection causes a long list of phenomena or lesions. The basic conflict of view with the majority of investigators will inevitably draw much unfavorable criticism. In order to justify the views stated, controversial matter has been included. This is regretted because it increases the size of the volume, and because some highly esteemed colleagues may erroneously regard such statements as personal reflections.

The conflicting views have served to delay publication. A belief so long and thoroughly entrenched as that of specific infectious abortion can not be overthrown quickly. Neither would the overthrow of what I believe an error be a gain unless a foundation were ready upon which a more valuable structure could be erected. I made the first open attack upon the specific infectious abortion theory in 1912, and that has been followed periodically from various angles. But external attack has not been as effective as internal disintegrating forces. The champions of a specific infectious abortion have admitted that at least several different species of bacteria may and do cause abortion in a given species of animal, and that the lesions caused by the several bacterial forms are not differentiable clinically or macroscopically. A most serious drawback to the theory has been its failure in practical application. It was announced twenty-five years ago that, since the cause of infectious abortion had been proven, it could be controlled. The twenty-five years which have elapsed have seen no progress in the control of abortion based upon the specific theory. The prevalence of abortion is greater today than at any prior date in history. During the past decade there has been developing gradu-

Preface vii

ally another view which appears more logical, is in harmony with the general principles of pathology, and is in full accord with all data recorded by the believers in specific infectious abortion. That portion of the volume designated "The General Genital Infections" must be regarded as the cornerstone ; if the principles it has been attempted to establish there break down, it fails as a systematic treatise. The principles which it is attempted to establish place the common and most destructive genital infections upon a plane analogous to wound infection. Various bacteria exist in the genitalia of both sexes of all ages and species. The virulence and variety vary at different times and in different individuals. They are modified by general health, coitus, pregnancy, parturition and other critical incidents in life.

The belief in a specific infectious abortiofi logically demands for the control of the disease the isolation of the pregnant female from all possible carriers of infections ; in this treatise it is held that physiologic reproduction is based upon coitus between two sexually healthy animals. The first is a hypothesis of despair, confirmed by lamentable failure over a period of twenty-five years : the latter a doctrine of hope, supported by success. Before publishing this treatise it was regarded as essential that the principles should have been tried thoroughly and proven successful in the crucible of practical clinical application. This has been a difficult task requiring unbounded and infinite patience under great discouragements and against opposition.

The treatise is inevitably very imperfect in every part, and those who are inclined to criticise will have excellent opportunity. But the volume was not made to cause or to avoid criticism. It is a first effort in a new field which, it is hoped, may be helpful to some and which may serve to awaken a new interest in the diseases interfering with reproduction in animals. The call of the hour to veterinarian and breeder is for increased efficiency of each domestic animal. The room for animal numbers is decreasing, while the demand for service in the production of milk, meat, labor or other products is increasing. Most of the great animal viii Preface

plagues which imperil the lives of adults have been brought under measurable control, but those infections involving the safety of the embryo are constantly gathering force. Yet it must be remembered that the sexual health of those animals desired for reproduction is the first basic need in animal husbandry. Reproductive efficiency in purebred cattle, swine, and horses, so far as can be estimated, has dropped below 60 per cent, of the ideal and continues to descend at a discouraging pace. The condition can be relieved only through conscientious and skillful work by veterinarians and breeders. The problem is difficult and the duration of the task infinite. It calls for the adoption of a permanent policy of guarding sexual health in animals — not of "curing" established lesions. The advancement of reproductive efficiency in the best animals is at present the greatest economic problem in veterinary medicine.

In a higher realm the study of genital diseases in domestic animals may be made of incalculable value in the elucidation of the basic principles of genital diseases in man. Aside from the specific venereal diseases of man, the genital infections are probably analogous to, and possibly identical with, the general genital infections of animals. What is true of the intra-uterine infections of the embryo in domestic animals is presumably equally true in principle of the human embryo. The veterinarian has opportunities for the study of the infections of the genital organs and embryos of animals wholly denied to practitioners of human medicine. The veterinarian has freely available in the abattoir the genitalia in health and in disease of thousands and millions of freshly slaughtered cattle, sheep, and swine of all ages and of both sexes. The females are pregnant and non-pregnant and the embryos are of all ages, diseased and healthy. Clinically the veterinarian can palpate the genital organs of the cow and mare freely per rectum and read the anatomical lesions of ovaries, oviducts and uterus as the blind read braille. The fetus can be manipulated, its movements in response to mechanical stimulation studied, and its physiologic function of swallowing its amniotic fluid recognized.

Preface ix

The new-born animal can be studied freely regarding the infections carried from the uterus, can be fed experimentally, and may be destroyed at will for examination. If the veterinary profession is fully to live up to its opportunities and discharge its obligations to the state, it must contribute its share to the advancement of the knowledge of disease. Nowhere else can it contribute more, nor as much, of value, as in the basic principles of the physiology, pathology and hygiene of reproduction.

Purely a clinician, I have been dependent upon others for bacteriologic and histologic facts. • In this field Drs. W. A. Hagan and C. M. Carpenter have rendered invaluable aid. Working first in my department and later in the department of pathology and bacteriology, they have extended every possible assistance. Similar help has been given by Dr. Herbert L. Oilman, at present in my department. The reader should undertsand the difficulty of securing knowledge regarding genital infections in animals. In general bacteriologists have not studied the genitalia of animals for infections, but for one specific infection, and have left unrecorded and unstudied all others. If the bacillus thought by the investigator to be the cause of infectious abortion was recognized, that was deemed final proof of it, and no other, caused the disease. Drs. Hagan, Carpenter, and Oilman have so far as practicable studied all bacteria found in the genital organs and their significance in the problem of reproduction.

My collaborator. Dr. W. W. Williams, has contributed greatly to the value of the treatise. Having devoted his entire energy for a number of years to the handling of genital diseases and the advancement of reproductive efficiency in purebred cattle, he has demonstrated with unusual clearness the value of the scientific handling of this group of infections. He has contributed especially the sections upon the surgery of the cervix and the genital infections of bulls.

W. L. Williams.

Cornell University Ithaca, N. Y.

April, 1921

Part I Diseases And Defects Not Attributable To

INFECTION

PAGE

Chapter I

THE ANATOMY AND PHYvSIOLOGY OF THE GENITALIA . .

The Genital Organs of the Male ... i

The Testicles and Their Excretory Ducts ...••.... i

The Vesicula vSeminalis, Prostate, and Cowper's Glands ... lo

The Penis 14

The Sheath and Prepuce , 15

The Genital Organs of the Female 18

The Ovaries 18

The Muellerian Ducts 22

The Oviducts 25

The Uterus 26

The Cervix 33

The Vagina • 36

Gartner's Ducts 39

The Physiology of the Genitalia 44

The Ripening of the Ovisac and Ovum 44

Estrum 47

Ovulation 49

Menstruation ' ' . . . 51

The Corpus Luteum of Estrum 52

Copulation .... 53

The Ejaculation of Semen 53

The Migration of Spermatozoa 54

Fertilization 55

The Migration and Implantation of the Ovum 55

The Corpus Luteum of Pregnancy 56

Chapter II The Clinical Examination Of The Genitalia 73

The Clinical Examin.'^tion of the Male Genitalia ... 73

The Testicles 74

The Epididymis 75

The vSeminal Vesicles, Pro.state, and Cowper's Glands .... 76

The Semen and Spermatozoa 77 xii Contents

The Clinical Examination of the Female Genitalia ... 79

The Examination of Vulva and Vagina 84

The Examination of the Cervical Canal and Douching of the

Uterus 99

■The Diagnosis- OF EsTRUM iii

The Diagnosis OF Pregnancy 113

Chapter III Artificial Interferences With Reproductive Functions 140

The Induction of Estrum 140

Artificial Insemination 143

Artificial Abortion 146

Chapter IV Arrests And Aberrations In Genital Development 151

Asexual or Bisexual Aberrations 151

Neuters or Freemartins 151

Hermaphroditism 157

Arrests in the Development of the male Genitalia . . . 160

Arrests and Aberrations in the Development of the Testes . . 160

Cryptorchidy r6o

Aberration in Position of Scrotal Testes 161

Arrest in Functional Development of Scrotal Testes, Fetal

Testes 161

Aberrations in the Development of the Penis 163

Congenital Defects of the Female Genitalia 163

Uterus Unicornis 165

Double Uterus, Double Cervix 165

Persistence of Median Walls of Muellerian Ducts in Vaginal

Area, Double Vagina 167

Imperforate Hymen, Persistent Hymen 169

Chapter V Miscellaneous Defects And Diseases Interfering With Fertility 172

Umbilic Hernia 172

Ventral Hernia 174

Horizontal Vulva 174

Stricture of Vagina and Vulva 175

Diseases of the Feet and Limbs 177

Paralysis, Plumbism * * 179

Torsion of the Testicle 180

Traumatic Orchitis 181

Tubal Pregnancy 185

Vaginal Hernia 185

Torsion of the Uterus 189

Pelvic Tumors and Calluses 190

Contents xiii

Chapter VI Systemic Diseases And Derangements Interfering

WITH REPRODUCTION 192

Physical Overwork 192

Starvation 193

Obesity 194

Idleness and Overfeeding 196

Sexual Excess 200

Onanism or Masturbation 203

Chapter VII Coital Injuries 205

Kicks and Fractures 206

False Copulation, Rectal Injuries ... 210

Laceration and Rupture of the Vagina 214

Coital Rupture of the Uterus 216

Coital Rupture of the Urinary Bladder 217

Vaginal Hemorrhage following Coitus 218

Urethral Hemorrhage in Stallion 218

Contusions of Neck and Withers 219

Penial Injuries 219

Rupture of Prepuce 223

Strangulated Hernia 225

Chapter XIV The General Infections Of The Genital Organs ... 356

I. INFECTIONS OF THE GENITAL ORGANS OF BULLS . . 358 Orchitis 375

Degenerative Orchitis. Destruction of Spermatogenetic Epithelium in Calves 375

Orchitis in Adult Bulls. Abscessation and Necrosis of Testicles 379

Epididymitis ■ 385

Degenerative Epididymitis of Calves 385

Arrest in Development ... 385

Chronic Indurated Epididymal Abscesses of Calves 386

Epididymitis of Adult Bulls 388

Infections of the Glands of the Pelvic Urethra 389

Spermato-Cystitis 389

Diseases of Prostate and Cowper's Glands 393

Balantitis. Balano-Posthitis. " The Granular Venereal Disease" 393

II. GENERAL INFECTIONS OF THE GENITAL ORGANS OF

HEIFERS AND COWS

Diseases of the Ovaries. Ovaritis 394

Cystic Degeneration of the Ovaries, Nymphomania 395

Intra-FoUicular Hemorrhage 409

Post-Ovulation Hemorrhage into the Follicular Crater. ... 411

Hemorrhagic Corpus Luteum . . 412

Cystic Degeneration of the Corpus Luteum 413

Hypertrophy of the Corpus Luteum 418

Persistent Corpus Luteum .421

Central or Embedded Corpus Luteum. The Corpus Luteum of Pyometra and of Retained Fetal Cadaver 422

Contents xv

Abscess of Ovary 424

Corpora Nigra 425

Par-Ovarian Cysts 425

TuBAiv Infections 426

Salpingitis, Pavilionitis, Adherent Ovary 428

P^-osalpinx. Tubo-Ovarian Abscesses 445

Hydrosalpinx. Dropsy of the Pavilion 448

Cysts in the Mesosalpinx 452

The Diseases of the Uterus of the Heifer Calf and Virgin Heifer 453

Intra-Uterine Infection and Endometritis .... 453

Pyometra 458

The Infections of the Gravid Uterus 462

Apical Eudometritis with Necrosis of the Fetal Sac 462

Diffuse Endometritis, with Atony of Uterine Walls. Dystocia 464

Cervical Endometritis 465

Uterine Gangrene 467

Placentitis 469

Peripheral Placentitis with Necrosis and Dehiscence at the

Periphery of the Cotyledons 469

Inter-Placental Hemorrhage with Desiccation of the Fetus.

IMummification 470

Incarcerating Placentitis 474

Necrosis of Cotyledons. Necrotic Placentitis 474

Adventitious Placenta 475

Calcification of Placenta 476

The Infections of the Ovum, Embryo and Fetus 476

The Death of the Fertilized Ovum . 476

The Death of the Embryo, with Survival of the Embr3-onic Sac.

Cystic Mole . . 477

Death and Maceration of the Embryo or Fetus 480

The Pyometra of Fetal Decomposition 480

Abscessatiou of the Gravid Uterus 484

Emphysema of the Fetus 487

The Observed Expulsion of the Fetal Cadaver. Abortion . . 487

The History of Abortion 488

The Prevalence and Frequency of Abortion 49 i

"Accidental Abortion" 495

"Food Abortion" 496

The Biology of Abortion 498

The Colon-Like Bacillus and the Micrococcus of Nocard 498

The Nodular Venereal Disease of Isepponi 499

The Bacterium Abortus of Bang 499

The Paratyphoid Bacillus of Moussu 511

The Spirillum of Smith and others 511

Miscellaneous Bacteria 511 xvi Co7itents

The Nature of Abortion 511

The vSymptoms and Diagnosis of Abortion 517

The Date of Invasion 518

The Control of Abortion 519

Diseases of the Puerperal Uterus 538

Uterine Hemorrhage. Uterine Hematoma . ; 539

Septic Metritis 554

Placentitis, Cotyledonitis. Retained Fetal Membranes . 560

Puerperal Tetanus 584

Puerperal Laminitis 585

Puerperal Meningitis 585

Post-Puerperal Uterine Infections 586

Pyometra 594

Uterine Abscess 601

Abscessation of Uterine Submucosa , . , , 604

Sclerotic Metritis 605

Pelvic Adhesions. Parametritis 606

Pyemia, Pyemic Arthritis 609

Pyemic Abscesses 609

Cystic Degeneration of Uterine Walls with Hydrometra . 611

Infections of the Cervix 614

Retention of Menstrual Debris, Cystic Uterus 640

Retention of Fetus from Cervical Adhesions 641

Retention Cysts of Cervix 642

Cervical Prolapse 642

Infections of^the Vagina 645

Vaginitis. The^Nodular Venereal Disease 645

Gangrene 647

Perivaginal Phlegmon 648

Cysts and Abscesses of Gartner's Ducts 649

The Infections of the Vulva 650

III. CONGENITAL INFECTIONS OF CALVES Dysentery Neonatorum, Cai,f Scours, White Scours, Cai.f

Pneumonia, Arthritis, Pyemic Abscesses 651

The Problem of the Genital Infections of Cattle as a

Whole] 687

The Assembling of Herds and the Addition of Cattle to

Existing Herds 688

Equipment 694

The Systematic Handling of Herds for the Control of

Genital Infections 697

The Genital Infectious of Cattle as an Economic Problem 708

Conte7its xvii

The Genitai. Infections of Cattle in their Relation to Human Health . . 709

Chapter XXIII The General Infections Of The Genital Tract. " Con- Tagious Abortion." 778 Infections Of The Genital Organs Of Stallions ... 782

Orchitis and Epididymitis 782

Diseases of Seminal Vesicles, Semino- Vesiculitis 785 xviii Contents

II. GENERAL INFECTIONvS OF THE GENITAL ORGANS OF MARES

Diseases of the Ovaries. Ovaritis 788

Cystic Degeneration. Nymphomania 788

Infections of the Gravid Uterus, Ovum, Embryo or Fetus.

Abortion 793

Diseases of the Puerperal Uterus, Retained Afterbirth, Retention of Non-Gravid Horn of Chorion, Endometritis, Puerperal Laminitis 799

Metritis. Metro-peritonitis 803

Post-Puerperal Infections 805

Uterine Abscess 806

Pyometra S07

Vaginitis . . 811

Vulvar Gangrene 8^3

III. CONGENITAL INFECTIONS OF FOALS 814

Septicemia of the Foal 814

Retention of the Meconium 814

Dysentery 815

Arthritis. Pyemia 815

Re-Opening of Urachus 820

Rupture of Tendons 824

Chapter XXV The General Infections Of The Genitalia

Prostatitis of Dogs. Abortion, etc 831

Chapter XXVI Venereal Disease Of Rabbits 833

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Chapter I THE ANATOMY AND PHYSIOLOGY OF THE GENITAL ORGANS

A. The Male Genitalia

The male genital organs consist of the testicles, epididymes, vasa deferentia, vesiculae seminales, prostate and Cowper's glands, and the penis with its sheath and prepuce.

Prior to the disappearance of the Wolffian bodies in the embryo, there appear near their anterior end at their median side, two parallel thickenings in the peritoneum designated the genital ridges, which by an elaboration of their epithelium ultimately form the genital glands. At first they cannot be differentiated, but they quickly assume definite sex characters and can be recognized as male (testicles) or female (ovaries) glands.

1. The Testicles and their Excretory Ducts

a. The testicles at first lie against the vertebral column, in close proximity to each other, between the anterior ends of the Wolffian bodies. The essential structures of the testicles, the tubuli seminiferi and the specialized cells elaborating the spermatozoa, are formed from the peritoneal cells of the genital ridges. The contiguous peritoneal areas draw over the genital ridges, perpetuating the general peritoneal surface while the glandular mass of the testicle lies outside or above the peritoneal cavity.

The Wolffian bodies soon disappear as independent structures. The anterior end of each Wolffian body later forms the head of the corresponding epididymis, becoming continuous with the proximal end of the testicle, upon its lateral

2 Diseases of the Geyiital Orga^is

side. The Wolffian duct, after the virtual elimination of the Wolffian body, undergoes elaboration to constitute the body and tail of the epididymis and the vas deferens.

The artery of the testicle derived from the posterior aorta, is at first very short, but with the descent of the gland into the scrotum, it becomes one of the longest unbranched arteries in the body. The artery with its satellite vein, nerves, and lymphatics, and the investing peritoneum, constitutes the vascular or spermatic cord, one of the three fundamental connections of the testicle with the body walls.

A second attachment of the testicle to the body wall consists of the fibrous, cord-like gubernaculum testis. It is formed at about the same date as the genital ridge and extends from that part of the external integument, which is to constitute the fundus of the scrotum through the inguinal space, internal inguinal ring, and thence outside the peritoneum, upward, forward, and inward across the tail of the epididymis to the posterior end of the testicle to which it is attached.

As the testicle increases in volume and weight, it drops down into the peritoneal cavity towards the internal inguinal ring. In its descent the three attachments of the testicle, the vascular or spermatic cord (artery, vein, nerves, and lymphatics), vas deferens, and gubernaculum testis, each drags with it the peritoneum which furnishes to each structure a double fold, thus maintaining the continuity of the visceral with the parietal peritoneum, resulting in three double peritoneal folds, as shown in Fig. 1. When the testicle descends into the scrotum, the gubernaculum shortens throughout its course. In solipeds the tension of the gubernaculum, prior to the complete descent of the testicle, exerts a degree of traction upon its scrotal attachment sufficient to cause a depression or dimple in the scrotum. The approach of the testicle to the internal inguinal ring is accompanied by an evagination of peritoneum through it anterior to the gubernaculum, to constitute the processus vaginalis, which eventually forms the parietal peritoneum of the scrotum. When the testicle descends, it and the spermatic cord carry

The Male Genitalia 3

down their peritoneal fold which extends from the gubernaculum below the origin of the spermatic artery in the lumbar region. It is attached anteriorly to the spermatic cord and posteriorly to the scrotal wall, to form the mesorchium which constitutes a membranous median partition in the posterior part of each scrotal sac from the fundus to the internal inguinal ring, as shown in Figs. 2, 3, and 4. The processus vaginalis, in everting, pushes before it on the lateral side the as yet invisible cremaster which quickly develops when the testicle descends into a bright red, highly functioning muscle. The scrotal sac thus consists of two distinct groups of tissues, the general integument composed of the skin and dartos and the intra-abdominal portion consisting of the parietal peritoneum and the cremaster muscle with the intervening fasciae. The two groups of structures remain easily separable throughout life. The surgeon in performing the ''covered operation," when castrating animals with scrotal hernia, avails himself of this distinction

Fig. I. — The Testicle and its Attachments. Right inguinal region and testicle of 24 hrs. colt. P, Processus vaginalis surrounded by a dotted line and containing a curved sound, .S" ; G, first portion of gubernaclum testis ; G^, second porlion of gubernaculum testis extending to the epididymis,^ ; £, epididymis ; G^\ gubernaculum extending from epididymis (globus minor) to the testicle ; 7] testicle ; A, testicular artery ; F, F, vasa deferentia ; B, urinary bladder ; C/A, umbilical arteries.

4 Diseases of the Getiiial Organs

and readily separates the two groups between the dartos and cremaster so that he may ligate the structures of intra-abdominal origin just at, or near to, the internal inguinal ring.

In domestic animals, except the elephant, the descent of the testicles into the scrotum is a prerequisite to fertility; otherwise, spermatozoa are not formed.

In the descent of the testicle, the gubernaculum shortens, the processus vaginalis develops, and the tail of the epididymis with the caudal end of the testicle traverses the inguinal ring followed by the body and head of the epididymis and cephalic end of the testicle.

The descent of the epididymis and testicle of ruminants is directly downward. The gland comes to rest with the tail of the epididymis and that portion of the testicle which was, in the embryo, the posterior end directed downward. The long axis of the testicle is perpendicular to the spinal column. The epididymis thus rests upon the postero-lateral face of the testicle, its head directed toward the internal inguinal ring, its tail at the distal end of the testicle. The vas deferens passes inward across the lower margin of the mesorchium and turns upward on the postero-median surface of the testicle closely applied to it. The epididymis and vas deferens are thus parallel and separated from each other by the mesorchium or peritoneal fold connecting the visceral and parietal layers. It is important to remember this arrangement of structures when examining clinically the testi' cles for evidences of disease.

In solipeds the cutaneous attachment of the gubernaculum testis is farther posterior and higher than in ruminants. This draws the tail of the epididymis upward and backward causing its head and the corresponding end of the testicle to tilt forward. The gland revolves through 90 degrees on its short axis and comes to rest with its long axis parallel to the spinal column. The vas deferens, instead of doubling back along the postero-median surface of the testis as in the ruminant, leaves the horizontal testicle immediately at the tail of the epididymis and passes obliquely upward and forward, to come in contact with the vascular cord in the inguinal canal.

The Male Genitalia

Fig. 2— Testicles of Bull.

Section through the posterior scrotal wall of the bull. The left testicle is fully exposed, tiie right is covered by the cremaster muscle and fascia and by the scrotal peritoneum. C, Cremaster muscle divided longitudinally ; S, spermatic cord ; E, head of epididymis ; E' , body ditto ; E", tail ditto.