274 THE HORSE. 



vessels specially set apart for that purpose. When it is considered 

 that the stomach, bowels, liver, pancreas, and spleen, are all occi- 

 pied almost solely in supplying the fluid with its grosser materials, 

 and that the heart, lungs, kidneys, and skin, are constantly engaged 

 in circulating it, supplying it with oxygen, and purifying it from 

 noxious salts and gases, its importance in the animal economy may 

 be estimated as it deserves. 



As it circulates in, or immediately after it is drawn from, ita 

 appropriate vessels, the blood consists of an opaque, thickish fluid, 

 composed of water, fibrine, albumen, and various salts, and called 

 Liquor sanguinis, colored red, by having suspended in it a quan- 

 tity of corpuscles of a peculiar nature, some being without any 

 color. When drawn from an artery or vein, and allowed to remain 

 at rest for a few minutes, a coagulation takes place, by which the 

 blood is separated into the clot (coagulum) and the serum. The 

 former is composed of fibrine, having entangled in its meshes the 

 corpuscles; and the latter is the liquor sanguinis, without its fibrine. 

 The blood corpuscles of the horse measure about the five-hundredth 

 part of a line in diameter, being considerably larger than those of 

 man, whose diameter is only the four-hundred-and-thirtieth part 

 of a line ; those of the ass being still smaller, though only slightly 

 so. As in all of the mammalia but the camels, these bodies are 

 circular flattened discs, and are of the same size (nearly) in all 

 animals of the same species, whatever may be the age or sex. Ac- 

 cording to Messrs. Prevost and Dumas, the blood of the horse con- 

 tains less solid matter than that of man, in the proportion of 9.20 

 to 12.92 in 1000 parts. The temperature is also iower by about 

 two degrees of the centigrade thermometer, the pulse slower in the 

 proportion of 56 to 72, and the respirations 16 per minute against 

 18 in our own species. The shade of color in the red corpuscles 

 depends upon the proportion of carbonic acid and oxygen com- 

 bined with them. If the former preponderates, a deep purple-red 

 is developed, known as that of venous blood ; while a liberal supply 

 of oxygen develops the bright scarlet peculiar to arterial blood. 

 The saline matters dissolved in the liquor sanguinis consist of the 

 chlorides of sodium and potassium (which comprise more than one- 

 half of the whole salts), the tribasic-phosphate of soda, the phos- 

 phates of magnesia and lime, sulphate of soda, and" a little of tho 

 phosphate and oxyde of iron. 



GENERAL PLAN OF THE CIRCULATION. 



The blood is circulated through the body, for the purposes 

 of nutrition and secretion, by means of one forcing-pump, and 

 through the lungs, for its proper aeration, by another; the two 

 being united to form the heart. This organ is therefore a com- 

 pound machine, though the two pumps are joined together, so as 



