PAET II. 



CHAPTER lU. 



THE BLOOD, ARTERIES, ANJJ VEINS. 



200. The Blood. 201. t^erum. 202. Crassamenttim. 203. Bed Cor- 

 jMiscIes. 204. White corjjuscles. 205. Coagulation of hlood. 206. Arterial 

 and Venous Wood. 207 . Colour of Blood. 201a. The Heart. 20Q. Arteries. 

 209. Veins. 



200. The Blood. 



Blood is essentially the aliment or food of the body. By it all }iai'ts 

 are sustained and replenished, whilst from it are drawn all secretions, 

 including all material required for the repair of wounds or injuries. Its 

 specific gravity is about 1"050 in health, but varies in certain diseases. 

 Its ordinaiy temperatm'e is about 99° Fahrenheit. In quantity the blood 

 is supposed to amount to about one eighth of the body. It contains 

 a variety of substances, but its ultimate analysis corresponds pretty 

 closely with that of flesh. Throughout life it is always circulating in 

 the heart, arteries and veins. The theory' of its circulation has been 

 desci'ibed above in Chapter 1. Its reaction is constantly alkaline. 



Blood consists of a clear fluid, principally composed of water, holding 

 in solution about eight per cent, of albumen and two or tliree parts in a 

 thousand of the elements of fibrin, with a small quantity of salts of potash 

 and soda, lime, magnesia and other matters. Floating in it also are 

 found red and white corpuscles, the red exceeding the w^hite in nxunber 

 as about three or four hundred to one in health ; vaiying from eight 

 hundred to one during fasting, but in certain diseases of the blood the 

 white corpuscles are gi-eatly increased in number. In addition to these 

 red and white corpuscles, the higher powers of the microscope reveal 

 numerous minute molecules or gi-anules similar to those found in lymph 

 and chyle. 



Blood is recruited from supplies of new material furnished by the pro- 

 cess of primary digestion in the alimentary tract. It also receives 

 matters from the atmospheric air ; and lastly, from the secondaiy diges- 

 tion, as that process is called, by which the tissues, which have served 

 their purpose and become effete, are absorbed into the blood before being 

 discharged from the system. 



Hence anything which interferes with the i)rocess of primary digestion. 



