72 DISEASES OF CATTLE. 



carry dark-red blood. The impure dark-red blood is collected from 

 the sapillary vessels and carried to the right auricle by the veins; it 

 passes down into the right ventricle and thence into the pulmonary 

 artery, and through its branches to the capillaries of the lungs, where 

 the carbonio-acid gas andother impurities are given up to the air in the 

 air cells of the lungs (through the thin walls between the capillaries 

 and the air cells), and where it also absorbs from the air the oxygen 

 gas necessary to sustain life, which changes it to the bright-red, pure 

 blood. It passes from the capillaries to the branches of the pulmonary 

 veins, which convey it to the left auricle of the heart; it then passes 

 through the auriculo-ventricular opening into the left ventricle, the 

 contraction of which forces it through the common aorta into the pos- 

 terior and anterior aortas, and through all the arteries of the body 

 into the capillaries, where it parts with its oxygen and nutritive ele- 

 ments and where it absorbs carbonic-acid gas and becomes dark col- 

 ored. (See theoretical diagram of the circulation, PI. VII.) 



The branches of certain arteries in different parts unite again after 

 subdividing. This reuniting is called anastomosing, and assures a 

 quota of blood to a part if one of the anastomosing arteries should be 

 tied in case of hemorrhage, or should be destroyed by accident or 

 operation. 



BLOOD. 



The various kinds of food, after being digested in the alimentary 

 canal, are absorbed and carried into the blood by the lymphatics, and 

 by the blood to the places where nutrition is required. The blood 

 takes from all parts of the body all that is useless and no longer 

 required, and carries it to the different organs where it is eliminated 

 from the body. It contains within itself all the elements which nour- 

 ish the body. 



The blood may be considered a fluid holding in solution certain 

 inorganic elements and having certain bodies suspended in it. To 

 facilitate description, the blood may be considered as being made up 

 of the corpuscles and the liquor sanguinis. The corpuscles are of 

 two kinds, the red and the white, the red being the most numerous. 

 The color of the blood is due to the coloring matter in the red cor- 

 puscles. The red corpuscles are the oxygen carriers. Both kinds 

 are very minute bodies, which require the aid of the microscope to 

 recognize them. The liquor sanguinis is composed of water contain- 

 ing in solution salts, albumen, and the elements of fibrin. 



The lymphatics, or absorbents, are the vessels which carry the lymph 

 and chyle in the blood. They begin as capillaries in all parts of the 

 body, gradually uniting to form larger trunks. Placed along the 

 course of the lymphatic vessels are glands, and in some situations 

 these glands are collected into groups; for example, in the groin, etc. 

 These glands are often involved in inflammation arising from the 

 absorption of deleterious matter. 



