sae i eae: Ae ESE S iota eget Sy ik | | / oe University Library SF 995.W25 domesticated bird iii iN Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924000942916 DISEASES OF DOMESTICATED BIRDS THE MACMILLAN COMPANY NEW YORK - BOSTON - CHICAGO - DALLAS ATLANTA + SAN FRANCISCO MACMILLAN & CO., Limrrep LONDON = BOMBAY + CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Lrp. TORONTO DISEASES OF DOMESTICATED BIRDS BY ARCHIBALD ROBINSON WARD, B.S.A., D.V.M. Director, Research Department, The Jensen-Salsbery Laboratories, Kansas City, Missouri AND BERNARD A. GALLAGHER, D.V.M. Bacteriologist, Bureau of Animal Industry, United States Department of Agriculture, Washington, D. C. WITH INTRODUCTION BY VERANUS ALVA MOORE, B.S., M.D., V.M.D. Professor of Comparative Pathology, Bacteriology and Meat Inspection, New York State Veterinary College at Cornell University, and Director of the College iNew Work THE MACMILLAN COMPANY 1920 — Wan rights reserved’ Y L, fey TP (i TALKS No, 5640 CopyriGcut, 1920, By THE MACMILLAN COMPANY Set up and electrotyped. Published, January, 1920 a al * Le le W Ww 25 () PREFACE The writing of this book has been prompted by a conviction held by the authors, regarding the magnitude of the losses experienced by poultry producers as a result of preventable infectious diseases and parasitic infestations. It is believed that the importance of these losses warrants the effort expended in presenting the essential facts concerning poultry diseases to meet the needs of veterinary practitioners, veterinary stu- dents and poultrymen. The title of the book indicates a slight broadening of scope beyond the field of a work on diseases of poultry. Material included deals with the ostrich, cage birds and wild birds in semi-domestication in zoological gardens. Chapters dealing with anatomy of birds, and killing of poultry have been included. The peculiarities of diseases of birds are indicated by the emphasis laid on certain features of the subject matter. In general, skill in diagnosing diseases of birds by observing symptoms is of less impor- tance than ability to recognize the identity of disease at autopsy. Symptoms are slightly characteristic, but autopsy material is freely available. Consequently more facts concerning details of gross lesions are given than those relating to symptoms. In many cases, particularly in the septicemias, symptoms and lesions are not dis- tinctive, and fine distinctions of etiology must be made by a bacteri- ologist. On this account considerable material useful to a bacteri- ologist alone has been included. Available sources of information are indicated in the references appended to each chapter and by specific references to authors in the text. Special acknowledgment is made for assistance obtained from Neumann’s “ Parasites et Maladies Parasitaires des Oiseaux Do- mestiques ” in the preparation of the chapters on parasites. Much material concerning the less common parasites has been drawn from this book and Neumann’s zoological nomenclature has been largely followed. A. BW, B. A. G. INTRODUCTION The statement is accepted that diseases are the greatest hindrance to the development of animal and poultry husbandry. Measures for the prevention, successful treatment or control of these maladies must come from those who understand their nature. It is grati- fying, therefore, that veterinarians, and others interested in the subject, are to have access to a volume dealing with the diseases of poultry, prepared by men of long experience in the study of the phenomena of disease. Likewise, poultry raisers will appreciate a treatise setting forth the known facts concerning the maladies which sooner or later may affect their flocks. A book of this kind will be of indispensable value in eliminating many of the miscon- ceptions regarding the diseases of poultry and in pointing out the things that are known and the precautions that must be observed in maintaining healthy flocks. The extent of the poultry industry in the United States is little appreciated by veterinarians. There is no other species in the animal kingdom that contributes to the material support of so large a number of people as the domesticated fowl. In addition turkeys, geese, ducks and pigeons are significant factors in food production while the ostrich and other birds play an important part in orna- mentation. In the Hartz Mountains, the raising of canary birds for the amusement and entertainment of people is an important in- dustry. The barnyard fowl plays a large part in the food supply of the country. The extent of the poultry business can be approximated from the fact that in 1910 there were 5,578,525 farms in the United States that reported a total of 280,350,000 fowls with a value of $140,205,000. With the prices at the present time, their value would be treble that of 1910. In 1915, the United States exported 20,784,000 dozen eggs but it imported over 3,000,000 dozen and over 8,000,000 pounds of egg yolks and frozen eggs. These figures indicate the large number of people who are financially interested in the poultry business. The raising of turkeys and other species is also significant. In 1910 there were in the United States 3,688,000 turkeys with a value vill viil INTRODUCTION of $6,605,000; 2,906,000 ducks valued at $1,567,000; 4,431,000 geese valued at $3,194,000; 1,765,000 guinea fowls valued at $613,000; 2,730,000 pigeons with a value of $762,000; 6,458 pea fowls estimated at $18,000; and 5,361 ostriches valued at $1,- 696,000. In 1915, this country imported ostrich and other feathers to the value of $2,500,000. Besides, there is a large business in song and other birds maintained as pets. In certain localities, the raising of one or more species of poultry constitutes the essential occupation of many of the people. The pro- ductivity of domestic fowls is greater than that of any other species of animals in proportion to their value. The price of the annual products from a flock of ducks, hens or turkeys may be many times larger than the cost of the original flock. There is no other form of animal life that suffers more from the ravages of disease than fowls. The losses from the general maladies are heavy and those from the infectious ones are sometimes appal- ling. Various estimates have been made of the annual losses occa- sioned by these causes. They vary from 10 to 30 per cent. Hens in particular suffer from a wide range of diseases and parasitisms. Some of these are veritable plagues and at times are the cause of serious losses. In 1903, while studying poultry diseases in a lo- cality where eggs and chickens were the chief articles of commerce, it was not unusual to learn of individual losses ranging from a few hundred to several thousand dollars due to roup or diphtheria. Other large flocks were decimated by tuberculosis. While it is easy to understand that heavy losses may occur in localities where fowls are kept in large numbers, it should be recognized that they are proportionately heavy in smaller flocks. In such circumstances, the death of a few hens is often the cause of much privation if not actual suffering among their owners who are dependent upon the products of their fowls for the necessities of life. The general diseases of poultry present many points of interest, although they have received relatively little attention. The general pathology of the feathered tribes is not well understood. Little seems to be known of their tissue reactions to injury. Their resist- ance to ordinary wound infections differs strikingly from that of mammals. Pasteur suggested that this might be due to their higher body temperature. On the other hand, the infectious diseases and parasitisms have been more carefully studied. The findings of many valuable researches are recorded on the nature of the more serious ones. Certain of them, such as bacillary white diarrhea and INTRODUCTION ix the parasitisms, have been elucidated sufficiently to enable veterin- arians or poultry owners to prevent them. Others that cause heavy losses, such as roup or diplitheria and tuberculosis, can be controlled. When this is done, millions of dollars worth of poultry that is now lost will be saved. This can be done as soon as the technical knowl- edge, now available, is utilized to its full extent. It is believed that veterinarians can render a valuable service to this heretofore professionally neglected, yet important industry, es- pecially in localities conspicuous for the raising of poultry. Be- cause of the relatively small value of the individual, and the large numbers to be dealt with, methods for preventing disease must be applied to the flock. With the exception of the more valuable birds, individual treatment may not be practicable, but the princi- ples of sanitation and the preventive measures are as helpful here as elsewhere in the raising of animals. Veterinarians should re- alize that the treatment, prevention or control of diseases in poultry, as well as in quadrupeds, is primarily an economic question and that a score of dollars saved by preventing or treating diseases in fowls is just as essential as the saving of a like amount in sheep or calves. This book, dealing with. the diseases and the parasites of poultry, will be of much aid to veterinarians who wish to render full service to their communities. V. A. Moors. TABLE OF CONTENTS CHAPTER I PAGE ANATOMY oF Birps . . . . wee ee ee ee eC CHAPTER II Hyciene aNnp SANITATION . . ww ee ee ee ee 20 CHAPTER III APOPLECTIFORM SEPTICEMIA AND SLEEPING DisEASE. . . . . . . 28 CHAPTER IV Fown @HOLERA, . «© «© 8» & # © © «© © 6 © 6 «© «© «© « 84 CHAPTER V Fow.t TypHow anp Smumar INFECTIONS. . . . . . ... =. 50 CHAPTER VI Bacmunary Wuite DiarRHEA . . . . . ee ee ee ee C88 CHAPTER VII FOWL: POAGUE @ os oe. Bo Sow Bo Bo wo we GP eh. a eS OE ae BE CHAPTER VIII Avian TUBERCULOSIS. . . . ee ee ewe ee eee 8B CHAPTER Ix Avian DIPHTHERIA AND Birp Pox . . . . ww ee ee ee C8 CHAPTER X ASPERGILLOSIS AND Favus . . . . . . « « «© e « « + « Lid CHAPTER XI Inrectious ENterRo-HEpATITIS oF TURKEYS. . ... .. . . 120 CHAPTER XII Cocciniosis & wie. GO cae het Te at Se! Ee ee ee TE CHAPTER XIII SpmocHeTosis AND Rare Inrectious Diseases . . . . . . . » 185 xi xii CONTENTS CHAPTER XIV LEUKEMIA AND PsEupo LEUKEMIA . CHAPTER XV GENERAL DISEASES CHAPTER XVI INTERNAL PaRasITEs . CHAPTER XVII EXTERNAL ParRASITES . CHAPTER XVIII InrectTious DIsEASES AND PARASITES OF THE OSTRICH . CHAPTER XIX Inrectious Diszases or GEESE AND Ducks . CHAPTER XX Inrectious Diseases or Canary Birps . CHAPTER XXI Tumors In Fow.s CHAPTER XXII ToxIcoLocy CHAPTER XXIII SurcicaL DIsEASES CHAPTER XXIV CAPONIZING CHAPTER XXV Kine Pouttry PAGE . 146 . 150 . 178 . 208 . 226 . 242 . 252 . 261 . 276 . 295 . 802 . 314 DISEASES OF DOMESTICATED BIRDS CHAPTER I ANATOMY OF BIRDS The structure of birds differs in many respects from that of mammals and deserves a special description. The aim of the authors is to bring to the attention of the veterinarian the more important differences which are observed in the structure of domesticated birds as compared with that of domesticated mammals. The subject will be considered under the following sub-divisions. 1. Skeleton, 2. Musculature, 3. Circulatory system, 4. Nervous system, 5. Ali- mentary system, 6. Respiratory system, 7. Urinary system, 8. Generative system, and 9. The skin and its appendages. SKELETON Skull. The bones of the skull become united shortly after hatch- ing and lose their individual identity except in the case of the as- cending processes cf the premaxillary and nasal bones which are not rigidly joined to the frontal bone but through their cartilaginous attachment permit the elevation of the superior mandible. The in- ferior processes of the premaxillary bone, the supermaxillaries and the palatine bones which form the roof cf the palate do not meet in the median line, with the result that the palate presents an elongated opening or cleft. Vertebral column. The cervical vertebrae vary in number in the different species. Statements of anatomists differ concerning the number, because of difficulties experienced in defining cervical and thoracic vertebre. The atlas or first cervical vertebra is ring-like in form and articulates with the occipital bone of the skull by means of a deep coneavity into which the condyle of the occipital bone is re- ceived. This articular arrangement and that of the other cervical vertebrae gives the head and neck great mobility. The articular sur- face is concave from side to side and convex in a dorso-ventral direc- tion on the anterior extremity of each vertebra, presenting a saddle shaped appearance. The posterior extremity is the reverse, that is, concave dorso-ventrally and convex from side to side. 1 2 DISEASES OF DOMESTICATED BIRDS Nasal Lachrymal Guadai ‘ Quadrate @ ce | “Occipital tee Sl Se é ; ---Metacarpus a pus Pygostyle “~Metatarsus Fic. 1. The skeleton of the fowl. (Bradley) The thoracic vertebrae are nearly always fused together by the con- solidation of their spinous and transverse processes. The first may be free and the last may be fused with the lumbar vertebre. The lumbar and sacral regions of the vertebral column show no special line of demarcation. The fourteen vertebre are consoli- dated into one bony mass which carries ridges on its ventral surface representing the transverse processes of the original independent vertebree. The coccygeal vertebre are seven in number. The last is the largest, is flattened on both sides and curves in a dorsal direction ANATOMY OF BIRDS 3 at the end. It is known as the’ pygostyle. The coccygeal vertebre are movable upon each other. Ribs. These bones articulate dorsally with the thoracic vertebra, and ventrally with the sternum by means of the inferior ribs, except in the case of the first two which do not reach the sternum. The last rib is often united to the one adjoining and does not connect with the sternum. Some of the ribs have flat uncinate processes which extend from the posterior border and lie over the external face of the following rib near its middle. The sternum is highly developed in birds and forms the floor of the thoracic cavity and to some extent, of the abdominal cavity. It is concave on its dorsal or internal face and convex on its ventral or external face. In fowls and pigeons a deep ridge extends along the median line of the ventral face. ~This is known as the brisket or keel. It serves to increase the area of attachment for the powerful breast muscles. The sternum of the duck and goose does not present as large a keel as that of the fowl and pigeon, but owing to the greater breadth of the sternum and more solid construction the area for muscular attachment is as great. In the fowl two long slender lateral processes are formed on each side as a result of deep notches which extend anteriorly into the body of the sternum. The lateral external process is shorter than the lateral internal process and covers the last two ribs with a broadened terminal bony plate. The lateral borders of the body of the sternum support articular facets for the reception of the inferior ribs. The anterior border presents an eminence, the episternal process to which the furculum (wishbone) is attached by a ligament. The articular surfaces for the coracoids are located on each side of the episternal process on the anterior border. The internal surface of the sternum exhibits several openings through which air is passed to the interior of the bony structure. Bones of the wing. These comprise the scapula, coracoid, and clavicle in the shoulder region; the humerus in the arm; the radius and ulna in the forearm; two carpal bones, the radio-carpal bone and ulno-carpal bone; one carpo-metacarpal bone, and three digits the second of which has two phalanges. The scapula is long, narrow, thin and curved like a sabre. It extends caudad over the ribs to near the pelvis. Anteriorly it is united with the coracoid with which it forms an articular cavity for the reception of the head of the humerus. The coracoid also articulates with the sternum by its ventral extremity. It is rod 4 DISEASES OF DOMESTICATED BIRDS shaped and extends in a posterior direction obliquely ventrad from scapular to sternum. The coracoid at its ventral extremity presents an opening for the passage of air to the internal air space. The clavicle is attached to the coracoid at its superior end. It extends ventrad and caudad and curves in to the median line at the point of the sternum where the two clavicles unite in a flattened plate and become attached to the episternal process by a ligament. The united clavicles form a V or U shaped bone termed the fork or furculum. This bone represents an elastic spring and serves to prevent the wings from approaching’ each other during contraction of the de- pressor muscles. The humerus is long in palmipeds and the galline, and short in the pigeon. It is stout, slightly curved and presents a pneumatic foramen near its articular head. The ulna is much larger than the radius and is separated from it except at the extremities, where the two are united by ligamentous bands. The olecranon process of the ulna is only slightly developed. The two carpal bones represent fusions in embryonic life, of the four bones of the proximal row. The distal carpal row of three bones fuse with the metacarpal bones. Bones of the leg. These are the pelvie or hip bone; the femur or thigh bone; the patella, tibio-tarsus and fibula in the lower leg region ; a tarso-metatarsal bone, and four digits. The pelvic bone is made up of three bones as in mammals, the ilium, ischium and pubis. It differs from the mammalian bone in that the pelvic girdle is not complete on the ventral floor, the two pubic bones failing to meet in the center to form the pubic sym- physis. ‘This arrangement facilitates the passing of the egg through the cavity. The ilium is the largest segment and extends along the vertebral column in the lumbar and sacral regions. It is consoli- dated with the last two thoracic vertebree and the lumbar and sacral vertebre, this extensive fusion giving the pelvis a rigidity which compensates for the lack of a pubic union. The ischium partly forms the side of the pelvic cavity. The pubis is mainly attached to the ischium along the lower border and bends inward to form the incomplete floor of the pelvic cavity. The ilium, ischium and pubis are united at the acetabulum or articular cavity for the reception of the head of the femur. The femur articulates at its distal extremity with the patella, tibia and fibula. The latter bone is united to the tibia, but does not ex- tend to its distal articulation. The tibia is comparatively long. ANATOMY OF BIRDS 4) It has two articular surfaces on its distal extremity which articulate with the tarso-metatarsal bone. The tarsus is absent in birds. In males the tarso-metatarsus exhibits a slightly curved conical projec- tion near the distal third for the support of the spur. Four digits articulate with the distal extremity of the tarso-meta- tarsus. Three are directed radially cephalad. The internal digit has three phalanges; the middle, four and the external, five. The fourth digit is directed caudad and has two phalanges succeeding a rudimentary first metatarsal bone attached to the metatarsus by fibro-cartilaginous tissue. The distal bone of each digit is covered by a horny claw. MUSCULAR SYSTEM In general the muscles of birds correspond to those of mammals, with such modifications as are most suited to the mechanism of avian structure. The tendency, especially in turkeys and fowls, is to- ward extensive ossification of the muscle tendons. This is partic-. ularly noticeable in the tendons of the legs but may also be observed in the wing and neck in some cases. The fowl and turkey also present a marked contrast in the appearance of the muscles of the breast and wings as compared with those of the legs. The breast and wing muscles are white, due to the relatively small amount of sarcoplasm in the muscle fibers. The red muscles are rich in sarco- plasm. White muscles are more powerful but have less endurance than red ones. Free flying birds have red pectoral or breast muscles. The pectoral muscles are two in number, the superficial or great and the deep or small pectoral. The former depresses the wing and the latter elevates it. These muscles are very massive. The great pectoral muscle is attached to the clavicle, to the sternal crest near its border, to the posterior lateral process of the sternum and to the last ribs. It is inserted into the lateral tuberosity near the head of the humerus. It is this muscle that propels the bird in flight. The small pectoral muscle originates from the portion of the ventral face of the sternum not occupied by the great pectoral and also from the clavicle and membrane between the latter and the sternum. Its tendon is inserted into the humerus opposite that of the great pectoral muscle after passing through the foramen trios- seum which acts as a pulley. This foramen is formed by the union of the scapula, coracoid and furculum. The diaphragm does not exhibit the muscular development of that 6 DISEASES OF DOMESTICATED BIRDS of mammals. It is principally membranous with fine muscular bundles attached to the ribs. Two thin, delicate membranes com- pose the diaphragm and divide it into two planes, a pulmonary and a thoracic-abdominal plane. The former is spread over the in- ferior face of the lungs and is attached to the ribs on its border. It assists in respiration. The thoracic-abdominal plane has its origin on the dorsal spine in common with the pulmonary plane. It is convex anteriorly and extends to the sternum, dividing the body cavity into a thoracic and an abdominal cavity. It also assists in respiration and is particularly concerned with the abdominal air sacs. The pectineus muscle assists in the mechanical flexion of the toes in the act of perching on the roost. It originates on a tuberosity of the hip bone in front of the acetabulum and is continued by a long thin tendon to a short distance distad from the head of the tibia where it joins the flexor perforatus of the three anterior digits. CIRCULATORY SYSTEM The heart of birds is cone shaped, short and wide in the ostrich, elongated and possessing a more acute apex in the common fowl. It is placed in the anterior extremity of the thoracic cavity. Three veins, two anterior vense cave and one posterior vena cava, terminate in the sinus of the right auricle. A peculiarity of the heart of birds is the absence of a tricuspid valve at the right auriculo-ven- tricular opening. Instead, a strong muscular fold which becomes closely applied to the ventricular septum during systole prevents re- gurgitation of blood into the auricular cavity. Two pulmonary veins empty into the left auricle. The left auriculo-ventricular opening is provided with a bi-cuspid or mitral valve. The pulmonary artery and aorta each has a semilunar valve. Arteries. The aorta gives off two innominate arteries, right and left brachio-cephalic, on leaving the heart and then passes over the right bronchus to become the descending or dorsal aorta. It con- tinues along the spine, giving off numerous branches, to the coccygeal region where it separates into three terminal arteries. The two carotids leave the innominate arteries and curve toward the ventral median line of the neck where they ascend in close prox- imity to each other to near the head. At the angle of the jaw each carotid divides into the external and internal carotid arteries. The arteries, especially those of the head and viscera, are distinguished ANATOMY OF BIRDS 7 by their frequent anastomoses. This is also true of the veins of birds. Veins. The blood is returned to the heart by three trunks, the two anterior vene cave and the posterior vena cava. The right jugular exceeds the left in size. The two communicate with each other by means of a cross branch at the base of the cranium. Lymphatics. The lymphatics of birds do not form two strata, a superficial and a deep seated, as in mammals. The latter only is observed. Lymphatic glands are few. The most conspicuous are located at the base of the neck and in the anterior thoracic cavity. They are replaced by plexuses of lymphatic vessels surrounding the principal blood vessels. From the aortic plexus arise two thoracic ducts which pass cephalad on the ventral surface of the lungs and terminate respectively in the jugular vein of the same side. NORMAL AVIAN BLOOD In birds as in mammals the blood is composed of a straw colored fluid or plasma in which float several types of blood corpuscles. One important difference between avian and mammalian blood, excepting the camel, is the presence of nuclei in the red corpuscles of the former. The formed elements or corpuscles are divided into two main divisions, the red cells or erythrocytes and the white cells or leucocytes. These elements vary greatly in number in different birds, and even in the same bird at different ages. Each cubic millimeter of an adult fowl’s blood contains approximately 3,250,000 red cells and 26,000 white cells, giving a percentage relation of 125 to 1. In certain pathologic conditions this relation is markedly changed, the red cells rapidly decreasing and the white cells increas- Ing in numbers. Red blood corpuscles or erythrocytes are straw colored, nucle- ated, oval, flattened discs, about 12 microns in length and 7.3 mi- crons in width. The nuclei take a deep blue stain with methylene blue, or Giemsa. The surrounding protoplasm takes a light yellow with methylene blue and a pink color with Giemsa’s stain. White blood corpuscles or leucocytes are nucleated, colorless cells, rounded or irregular in form. They exhibit ameboid movement in the blood stream, some being more actively motile than others. The variations in their size, character of the nuclei, pres- ence of granules and character of the inclosed granules differentiate these cells into five varieties. These varieties with their percentage ratio are as follows: 8 DISEASES OF DOMESTICATED BIRDS Small mononuclear leucocytes (lymphocytes) ........ 40 Large mononuclear leucocytes ......+. sess eee eeeeers 18 Polymorphonuclear leucocytes ......+.-eeeeee eee 35 Eosinophiles ......c. cee cee ccc cece cee cen cnn eeeeere 4 Mast cells? aciecs asucessabitee Wen es tetas ae elece eee 3 Lymphocytes. In these blood cells the nucleus is rounded or oval and almost completely fills the cell. It stains a deep blue with Giemsa. The narrow band of cell body stains a lighter blue and is not readily differentiated from the nucleus by ordinary staining. The lymphocytes are from 5 to 7 microns in diameter. Large mononuclears have a round or oval nucleus surrounded by a well defined border of cell protoplasm. The nucleus takes a deep blue stain, the cell body a pale blue. The cell diameter is 10 to 15 microns. Polymorphonuclears have the appearance of having several nu- clei held together by threads or nuclear bands. They contain con- siderable protoplasm inclosing rod shaped or rounded granules. The nucleus stains blue, the protoplasm, a lighter color and the granules violet or brownish red with Giemsa’s stain. Diameter, 10 to 15 microns. Eosinophiles have an irregular nucleus. The cell protoplasm is filled with rounded granules which stain a bright red with Giemsa’s stain. The nucleus takes a blue stain and the cell body a pale blue. Diameter, 12 microns. Mast cells have a lobulated nucleus which stains a deep blue. The cell protoplasm takes a pale stain. The granules are small and rounded and stain a dull violet with Giemsa and a deep blue with methylene blue. Diameter, 8 to 10 microns. Other blood cells of less importance which may be observed are as follows: Blood platelets are small colorless dises with granular centers. They are 3 to 4 microns in diameter and are usually found in small heaps of 6 to 8 cells. Shadow cells contain a rounded or broad oval nucleus which takes a deep blue stain. The cell body is colorless and not well de- fined or irregular in outline. These apparently represent red blood corpuscles undergoing degeneration. The stroma of the corpuscle loses its pigment, becomes colorless and gradually disappears leaving the nucleus partially or wholly separated. They are especially nu- merous in pathologic blood. Microblasts and macroblasts are found in the blood of young ANATOMY OF BIRDS 9 fowls. These represent red corpuscles which are smaller and larger respectively than the average red corpuscle. Myelogenous leucocytes appear frequently in young fowls. They are like mast cells except that their protoplasm is vacuolated. NERVOUS SYSTEM The nervous system of birds, with few exceptions, corresponds with that of mammals. However, there are several modifications which are of considerable interest. The cerebral hemispheres of the brain are well developed but have a smooth surface in contrast to the convoluted surface observed in the cerebrum of mammals. The cerebellum is conspicuous by the smallness of its lateral lobes. ‘The optic lobes are placed in a lateral inferior position at the sides of the cerebellum. The large size of the optic chiasma and nerves indicates the paramount importance of the visual apparatus. The diameter of an optic nerve is equal to that of the spinal cord in its dorsal region. The olfactory lobes are relatively small. The hippocampi are absent in the cerebrum of birds. An important fea- ture of the nervous system of birds is the absence of nervous tracts leading to the spinal cord from the cerebrum. The cerebrum does however exert an influence over the rest of the nervous system threugh its nervous tracts connecting it with the other divisions of the brain. The anatomical evidence of the absence of nervous tracts between the cerebral hemispheres and the spinal cord is supported by the absence of any marked defects of movement succeeding the removal of the cerebrum. The fowl so treated, on recovery from the operation, is not sensitive to light or sound. It fails to pick up erains and must be fed. Movement is not interfered with as the bird constantly walks about aimlessly. Its avoidance of obstacles shows that it is guided by some obscure means. Ability to perch and to maintain its balance is not lost. The weight of the brain of a medium sized fowl is ten grams. The spinal cord of birds extends into the coccygeal vertebra. It is cylindrical throughout its length except in the sacral and cervico- dorsal regions where two expansions are noted. The dorsal columns of the cord diverge from each other in the sacrum to form the cavity known as the sinus rhomboidalis which represents a ventricular dilatation of the spinal canal. The brachial plexus is formed by the last cervical and first two dorsal spinal nerves in ducks and geese and 10 DISEASES OF DOMESTICATED BIRDS by the last three cervical and first thoracic spinal nerves in fowls, turkeys and pigeons. It furnishes branches to the pectoral region and wing. The pelvic region and legs are supplied by the lumbo- sacral plexus which is formed by two lumbar and four sacral spinal nerves. The spinal nerves vary in number according to the number of vertebrae present in each species. They arise from the spinal cord by two roots. The anterior or ventral root is motory, the posterior or dorsal, sensory in function. The ganglia on the latter are propor- tionately large. ALIMENTARY SYSTEM The alimentary system of birds differs to a considerable degree from that of other animals. There is no provision for mastication of food in the mouth owing to the absence of teeth. The food is taken up by the beak and is immediately passed by the tongue into the pharynx. From there it enters the esophagus and is carried to the crop where it is stored, partially softened, and slowly passed on to the proventriculus or glandular stomach. The gall bladder is absent in the pigeon and ostrich and occasionally in the guinea fowl. Mouth. The mouth is triangular in shape in such birds as the chicken, turkey, pigeon and canary. In the duck, goose and ostrich the mouth is comparatively long, with parallel borders and rounded anterior extremity. The roof of the mouth or hard palate is di- vided in the median line from near its anterior extremity to the pharynx, thus allowing free communication with the nasal passages. The soft palate observed in mammals is absent. The pharynx is relatively voluminous and permits the passage of large grains, or food masses. On its floor is the entrance to the larynx. The esoph- agus lacks the well developed muscular wall of mammals but rela- tively has a much greater diameter. Crop. Gallinaceous birds possess a crop or ingluvies which rep- resents a dilatation of the esophagus near its entrance to the thoracic cavity. Its wall, like that of the esophagus, consists of an outer membrane, a longitudinal muscular layer, a circular muscular layer, and an inner mucous membrane. Passage of its contents to the first stomach is aided by a wide circular muscle in the subcutaneous tissue surrounding the crop. Palmipeds, such as ducks and geese, are not provided with a distinct crop. Instead, the cervical portion of the esophagus may become greatly distended in such a manner as to form a long fusiform reservoir. Fic. 2. Diagrammatic representation of the principal internal organs of the ‘fowl. 1, tongue; 2, pharynx; 3, up- per portion of esophagus; 4, crop; 5, lower portion of esophagus; 6, proven- triculus; 7, gizzard; 8, origin of duo- denum; 9, first branch of duodenum; 10, second branch of duodenum; 11, origin of floating portion of small in- testine; 12, small intestine; 12’, ter- minal portion of small intestine; 13, free ends of ceca; 14, origin of ceca; 15, rectum; 16, cloaca; 17, vent; 18, mesentery; 19, left lobe of liver; 20, right lobe of liver; 21, gall bladder; 22, spleen; 23, pancreas; 24, lung; (Heart not shown but located approxi- mately here) ; 25, ovary; 26, oviduct; 27, kidney; 28, ureter; 29, upper larynx; 30, trachea; 31, lower larynx or syrinx; 32, bronchus; 33, cleft palate; 34, common ori- # fice of eustachian tubes. (Redrawn from Chauveau, with slight additions) 11 12 DISEASES OF DOMESTICATED BIRDS In pigeons the crop is divided into two lateral pouches. In both male and female, marked changes take place in the mucous mem brane shortly before the young are hatched. The membrane becomes thickened, epithelial cells are rapidly proliferated, undergo fatty degeneration and lead to the formation of a milky fluid which accu- mulates in the depressions between the ridges of the mucosa. This fluid is used to feed the young during the first days of life. A certain amount of fluid is secreted by the alveolar glands of the esophagus which together with the water consumed serves to soften grains to some extent and also to produce a slight fermentation of the crop contents. The crop has no secretory glands other than mucous glands. It is connected with the proventriculus or first stomach by a continuation of the esophagus which passes into the thoracic cavity and along the ventral face of the left lung. Proventriculus.. The proventriculus is small and fusiform in shape. Its walls are thick and contain numerous secretory glands which pour out gastric juice. The food is not held in the proven- triculus to be digested but after becoming saturated with the gastric secretion is forced into the gizzard where it is triturated by the powerful muscles of this organ with the aid of pebbles picked up by the bird. Gizzard. The gizzard or ventriculus bulbosus is a dense, mus- cular organ, flattened on two surfaces, with rounded border. In- ternally it is lined by a thick, tough, corrugated membrane which incloses a cavity of considerable volume, in which may be found food in various stages of disintegration and numerous pebbles, or bits of stone. Secretion of gastric juice also takes place in the gizzard according to Jobert. However, this organ acts principally in a mechanical way to grind the food and serves as a substitute for teeth. Its more highly developed in grain eating birds than in those subsisting principally on fish or animal food. In strictly carnivorous birds such as eagles, or hawks, the dense muscular wall is absent, or is limited to a portion of the organ, the remainder consisting of a membranous cul-de-sac. When reduced to a semi- fluid mass the food is released into the duodenum or first portion of the intestine, which joins the gizzard at a point near the entrance of the proventriculus. Intestines. On leaving the gizzard the duodenum extends pos- teriorly, bends on itself and returns to near its origin. Between its two parallel branches rests the pancreas which gives off its secretion into the lumen of the duodenum near its termination. ANATOMY OF BIRDS 13 The pancreatic juice acts on the starchy material while the secre- tion of the proventriculus acts on the proteins in the food. Suc- ceeding the duodenum are, according to some writers, the other two divisions of the small intestine, the jejunum and ileum. These form several convolutions and are continued by the rectum to the cloaca. At the point of juncture of the small intestine and rectum, in certain species of birds, are found two elongated diverticula lead- ing from the intestine. These are the ceca or blind pouches. In grown fowls and turkeys they are from 4 to 7 inches in length and may be distended to a diameter of 14 to 34 of an inch. Especial importance is attached to them because of the fact that they are the seat of marked lesions in coccidiosis of chickens, and of turkeys, and in infectious entero-hepatitis of turkeys. In some species of wild birds, the ceca may reach a length of 10 inches while in others they are absent or merely rudimentary. Their function is apparently the retention of food material which has not been absorbed in passage through the small intestine. The cloaca serves as a common cavity for the entrance of the intestine, ureters, oviduct in the female, and vasa deferentize in the male. It is divided into three parts. The rectum enters the first part, the ureters and genital canals open on the lateral faces of the second and the bursa of Fabricus, a blind sac or glandular cavity, opens on the dorsal wall of the third or outer division. The bursa of Fabricus may disappear in adults. The one oviduct in the female opens on the left side of the second division. The material from the intestine and ureters is held in the cloaca to form the character- istic droppings and is then passed out through the anus or vent. Mucosa of the alimentary canal. The alimentary canal is lined internally by a mucous membrane which is thick, and com- posed of many layers of cells in the mouth, pharynx, esophagus and crop. The mucosa is thin, and composed of one layer of columnar epithelial cells in the proventriculus, gizzard and intestine. In the gizzard the membrane is covered by a horny surface layer. In the submucous tissue of the mouth and pharynx are found several pairs of glands. These, however, are not considered as true salivary glands but produce a mucous secretion. The esoph- agus exhibits numerous alveolar secretory glands in the submucous tissue. The glandular stomach is conspicuous for the layer of tubular secretory glands which are set perpendicularly to the mu- cous m~™brane and which pour their secretion of gastric juice into the interior of the stomach. Over the mucous membrane of the 14 DISEASES OF DOMESTICATED BIRDS gizzard is a tough horn-like covering formed by the hardening of the products secreted by the underlying simple glands. The mucous membrane of the intestine presents innumerable cylindrical elevations known as villi. It is through these that the digested food is assimilated and carried by means of the chyle- vessels or lacteals to the portal vein and thence to the liver. Nu- merous goblet cells for the secretion of mucin are present in the villi. Liver. This organ is dark brown in color and composed of a right and left lobe, the former being the larger. The right lobe has a gall bladder on its ventral surface, while the bile from the left lobe is poured directly into the duodenum through a separate bile duct, the hepatic or choledic duct, which empties a short dis- tance behind the two pancreatic ducts. The cystic duct opens caudad of the hepatic duct and drains the gall bladder. Pancreas. This organ is long, narrow and lobulated. In color it is pale red. It is highly developed in birds and occupies the space between the two branches of the duodenum. Two or some- times three ducts carry its secretion into the ascending arm of the duodenum near its extremity and just anterior to the hepatic duct. RESPIRATORY SYSTEM The organs of respiration in birds differ markedly from those of mammals. They resemble more nearly the reptilian type of formation. Air passages. The nostrils are represented by two narrow openings at the base of the upper mandible of the beak. The nasal chambers are short and narrow and are separated by a septum which is partly bony and partly cartilaginous. The turbinated bones of mammals are represented by three cartilaginous structures. The nasal cavities open into the mouth by a common, elongated slit in the median line of the hard palate. Cavities known as the sub- orbital or infraorbital sinuses occupy a position on either side of the head. They communicate with the nasal cavity by narrow passages which extend from a comparatively low level in the sinus, upward into the nasal cavity. The arrangement prevents natural drainage of the sinuses. Birds possess an upper and a lower larynx. The former cor- responds to the larynx of mammals but serves only as an opening for the passage of air. An epiglottis is absent but its function is ANATOMY OF BIRDS 15 assumed by two lateral lips which close the laryngeal opening dur- ing the passage of food through the pharynx. The inferior larynx, or syrinx, is the voice organ. It is located in the anterior thorax at the division of the trachea into two bronchi. The end of the trachea, in fowls, is compressed from side to side and forms the wall of the syrinx. In certain birds the syrinx is complicated in structure and may be formed of a number of tracheal rings ex- panded to form large bony cavities. Sound is produced by the vibration of membranes within the walls of the lower larynx. The trachea is long in birds and its cartilaginous rings are com- plete. In the bronchi the cartilaginous rings are incomplete, a portion of the wall being formed by a membrane. The bronchi enter the lungs at the anterior extremities, become membranous and give off branches to these organs and to the air cells of the thorax and abdomen. The lungs are pale or bright red in color and of a spongy tex- ture. They are closely applied to the dorsal surface of the thorax and present several deep indentations into which the ribs fit. The ventral surface is smooth and is covered by a fold of the diaphragm. Only a small portion of the thoracic cavity is occupied by the lungs. Air sacs. These are membranous receptacles into which the air is carried by terminal branches of the bronchi. Through these branches the cells are in direct communication with the lungs. They also, with certain exceptions, communicate with canals or spaces in the various bones, to which they supply air. The membranous wall is composed of two delicate layers, an external serous and an in- ternal mucous layer. The latter is a continuation of the mucosa of the bronchi, the former is regarded as a reflection of the peritoneum and pleura. Nine air sacs are found in the thoracic and abdominal cavities. The single anterior thoracic air sac surrounds the inferior larynx, bronchi and large blood vessels of the region. It receives air from the anterior part of the lungs by two openings and com- municates with deep seated air cells of the neck and with the cla- vicle, coracoid, scapula and sternum. Two lateral thoracic sacs receive air from the internal edge of each lung opposite the base of the heart. They transmit air currents to the air cells of the axillary region, vertebre, ribs and humerus. The diaphragmatic air cells are four in number, two anterior and two posterior. They are inclosed between the two diaphragmatic folds. Air is received from the lungs but is not communicated to bony structures from these. Two abdominal air sacs each receive a long voluminous bron- 16 DISEASES OF DOMESTICATED BIRDS chial branch which leaves the respective lung on its posterior in- ferior surface. These sacs extend from the lungs to the cloaca and are the largest in the body. They supply the bones of the pelvic region and femur in those species in which these bones are aeri- ferous. The femur of the pigeon and the humerus of the ostrich have no air spaces but retain their marrow. URINARY SYSTEM The urinary tract is composed of two kidneys each drained by a ureter lying along its ventral face and proceeding caudad to empty into the cloaca posterior to the terminus of the rectum. The kid- neys are elongated, reddish brown bodies divided into three prin- cipal lobes. They are closely applied to cavities in the pelvis on each side of the spinal column. ‘These organs are not divided into macroscopically visible cortical and medullary zones as in mammals but have a homogeneous structure. In texture they are quite soft and rupture easily when pressed by the finger. The ureter does not originate in a renal pelvis but is formed by the union of several uriniferous tubules along the ventral face of the kidney. Its course may be traced by the white color of the urates which it carries, a material corresponding to the urine of mammals. GENERATIVE SYSTEM The male generative organs consist of two testicles each provided with a vas deferens or excretory duct. The testicles are oval shaped organs situated in the sub-lumbar region at the anterior extremities of the kidneys. They vary greatly in size at different seasons, but show a remarkable development during the breeding season. The two vasa deferentiz pass along the kidneys by the side of the ureters, exhibiting transverse convolutions along their course. Each opens on a small papilla situated in the uro-genital division of the cloaca. The base of each papilla is surrounded by a plexus of blood vessels which serve the purpose of an erectile tissue during coitus. In the drake and gander a long single penis is developed. The female generative organs consist of a single ovary and an oviduct situated on the left side of the abdominal cavity. The right ovary and oviduct usually fail to develop. Occasionally a rudi- mentary right oviduct is present. In one actively laying hen Gal- lagher observed a right oviduct which was nearly as long as the ANATOMY OF BIRDS 17 left oviduct and equally voluminous. Its anterior extremity ex- hibited an infundibular membrane in contact with the ovary. Pos- teriorly it opened into the cloaca opposite the left oviduct. The appearance of its mucous membrane suggested that it was capable of functionating. The ovary is placed in the left sub-lumbar region, opposed on its: superior surface to the ribs. In fowls it contains from twelve to fifteen hundred germ cells in various stages of development from microscopic granules to fully formed yolks in functionating ovaries. The oviduct terminates in the urogenital division of the cloaca just anterior to the left ureter. It is divided into five regions, each of which has a specific function. The first region, the infundibulum, is a delicate membrane of a funnel-like form which receives the ovum. Succeeding this is the part secreting albumen followed by the isthmus which secretes the shell membrane. The uterus or fourth region forms the shell. The last region, the vagina, is short and is provided with a sphincter muscle at its entrance to the cloaca. SKIN AND ITS APPENDAGES The skin of birds is without sweat glands. There are some small glands in the exterior passage of the ear, which secrete an unctious fluid. There is also a protruding glandular organ located above the coccyx between the tail feathers and known as the uropygium or rump gland, an organ peculiar to birds. It is round or oval in form and is divided into two halves by a medial septum. The exit passage is through a teat-like cone which projects above the level of the skin. Two external orifices are observed in the gland of the duck. In hens the gland is about the size of a pea, in geese about as large as a hazel nut and in the swan about an inch and one half in length. Its function is to secrete an oily fluid for water-proofing and dressing the feathers. The secretion is taken up by the beak and spread over the plumage. The feathers are complicated modifications of epidermic struc- ture. Each feather is composed of a quill, a shaft and a vane. The quill is embedded in a feather follicle of the skin and extends outwardly to the point where the barbs of the vane arise. It has an opening at its base for the reception of the dermal papilla and another opening at its point of junction with the vane. The shaft continues the quill to the extremity of the feather. The vane con- sists of two rows of barbs which arise on opposite sides of the shaft. 18 DISEASES OF DOMESTICATED BIRDS These barbs each carry two rows of barbules which interlock with those of adjoining barbs. The feather is elevated by a small muscle located in the skin at the root of the quill. The comb and wattles of fowls and the caruncle of turkeys are developed from the skin. INCUBATING PERIODS The length of time necessary for hatching eggs by natural incu- bation shows some variation. The normal period for the common hen is 21 days but this period may be shortened to 19 or 20 days by warm weather and unusually constant brooding by the hen. On the other hand, if the eggs have been abandoned and allowed to cool for a time, hatching may be delayed for several days. These varia- tions doubtless occur in the case of other birds. The incubation periods of various birds, subject to variations as explained are as follows. TasBLe I.— Incupatine PEriops MAGI