DISEASES OF THE ORGANS OF CIRCULATION 61 



Physiology. — ^The blood transports the oxygen and the fluid 

 and sohd nutrients (albumin, fats, carbohydrates, salts, and water) 

 to the tissues and organs and carries away the decomposition 

 products of metabolism, especially the carbon dioxide (lungs) and 

 the fluid and solid excretions (kidneys, Uver, intestinal glands, 

 cutaneous glands). The most important morphological elements 

 of the blood are the red and white corpuscles (the blood-platelets 

 are regarded by some as products of the decomposition of the 

 white blood-cells, by others as haemoglobin-free bodies from the 

 interior of the red blood-cells). The red blood-cells (erythrocytes 

 without nuclei) are derived from the red bone marrow. They are, 

 on account of the haemoglobin they contain, the carriers of oxygen 

 and form about one-third of the volume of the blood. A cubic 

 millimetre of horse's blood contains seven to eight million red 

 blood-cells. The white blood-cells (leucocytes) originate in part 

 from the red marrow of bone (granular leucocytes) and in part 

 from the lymph glands and spleen (lymphocytes without granula- 

 tion). They are much less numerous than the red blood-cells, 

 there being only one white corpuscle to 350 red; one cubic milli- 

 metre of horse's blood contains 9,000 leucocytes. Their functions 

 are manifold: fat resorption in the intestines, emigration, phago- 

 cjrtosis, immunization in inflammatory and infectious diseases and 

 histogenetic activity in healing of wounds and in cicatrization. 



The reaction of the blood is alkaline (KHCO3), corresponding 

 to a 0.2 to 0.4 per cent, soda solution. The most important chemi- 

 cal constituents are the proteids: haemoglobin, serum albumin, 

 serum globulin, nucleo-albumin, albumoses, peptone, lecithin and 

 protagon; the fats: stearin, palmatin and olein; the carbohydrates: 

 grape sugar and glycogen; the pigments: haemoglobin and bili- 

 rubin; and the salts: sodium, potassium, calcium, magnesia, iron 

 and ammonium combined with chlorine, carbonic acid, phosphoric 

 acid and sulphuric acid. The potassium salts are contained in the 

 blood-cells, the sodium salts in the blood-serum. In herbivora the 

 carbonates, in camivora the phosphates, predominate. 



The quantity of the blood is equal to about one-thirteenth of 

 the body weight; the relative amount is greatest in the horse (one- 



