File:Cyclopedia of farm animals (1922) (20800216916).jpg

Title: Cyclopedia of farm animals
Identifier: cyclopediaoffar00bail (find matches)
Year: 1922 (1920s)
Authors: Bailey, L. H. (Liberty Hyde), 1858-1954, ed
Subjects: Domestic animals; Animal products
Publisher: New York, Macmillan
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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I'HYSIOLOGY OF DOMESTIC ANIMALS 25 The gizzard or second stomach is the triturating apparatus. It is an ovoid organ with very thick muscular walls and contains small pebbles and sand necessary to crush the food. An acid secre- tion is also poured out here and proteid digestion begins. In flesh-eating birds the crop is absent and the gizzard thin-walled. The food of these fowls requires no trituration. The orifice between the gizzard and small intestine is small and large indi- gestible masses of food unable to pass through are vomited up. The solvent ac- tion of the gastric juice is strong. In the intestine the food is acted on by the intestinal juice, the bile and the pancreatic secretion poured into the duo-
Text Appearing After Image:
Fig. 27. The digestive apparatus of a common fowl. 1, tongue; 2. esophagus, first part; 3, crop; 4, esophagus, second part; 5. succentrie ventricle; 6, gizzard: 7, origin of duodenum; 8, second blanch of duodenal flexure; 9, origin of floating part of small intestine; 10, small intestine: 11, caeca: 12, insertion of ca?ca; 13, rectum; 14, cloaca; 15, pancreas; 16, liver; 17, gall-bladder; 18, spleen. denum. Villi for absorption are numerous. Fowls have two club-shaped ceeca six to eighteen inches long ; they secrete a macerating fluid. The rectum terminates inside of the anal opening in a cavity called the cloaca, a dilated receptacle for the feces, the urine, the egg from the oviduct and the semen. The cloaca also lodges the penis. Circulation of the blood. The circulation of the blood in fowls offers few practical differences when compared with other domestic species. The blood is characteristic in that the red blood cell is bi-convex, neucleated and oval instead of round. The temperature of the blood is much higher than in mammals, being 41° to 42° C, and even 44° C. in health. For this reason poultry are immune to certain diseases, as anthrax, whereas, when surrounded by a cold chamber or swimming in cold water so as to lower the tem- perature, such immunity ceases. Respiration. The disposition of the respiratory organs shows some marked peculiarities. The last ring of the windpipe is disposed to resemble a second larynx, which in song-birds is the source of vocal sounds. The lungs are small, fastened to each side of the backbone, and only partly fill the chest. A modi- fied diaphragm is present. Most remarkable is the air-reservoir or air-sac system in the avian species. The large air-sacs are situated between the backbone and the organs in the thorax and abdomen. They are connected with the lungs through the bronchial tubes. Peripherally they are continued by means of membranous tubes into a series of smaller sacs in the pelvis and be- tween the muscles of the thigh, shoulder and arm. Here they enter small orifices in the bones and open into air-sacs in the marrow cavity. Bones so hol- lowed are the vertebras of the backbone, breast- bone, ribs, pelvis, thigh, shoulder-blade and arm bones. Contraction of the surrounding muscles com- presses the air-sacs and expels the air through the lungs; when the compression ceases, the air is again sucked in and the sacs distended. Inspiration thus is passive and expiration active, and the air during both acts passes through the lungs. The inter- change of oxygen and carbon dioxid is similar to that in the lungs. The air-sacs render the body lighter, promote equilibrium during flight and increase the range and power of (HJ the voice. Reproductive functions. The testicles, oval in form, are situated against the roof of the abdomen opposite to the last three ribs and in front of the kidneys. They lie close to a large vein, the vena cava, which can be readily torn in caponizing. There are no seminal vesicles. The semen passes through the spermatic ducts into the cloaca. In the crowing species the penis is only a small eminence at the cloacal margin, and is traversed by a furrow through which the semen flows. In dueks and geese it is of a corkscrew form. During copu- lation the anus of the male is placed against the cloaca of the female. In the female there is one ovary, the left, the right being — 28 nearly always atrophied. The Crop and ^zali situation is the same as that 0f fowl. -

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