THE BLOOD 



431 



development, maintenance, and repair, whilst it is in addition charged with 

 the vivifying oxygen it has absorbed at the lungs. On the other hand, it 

 carries away from each part the products of disintegration and decay, and 

 conducts them to the organs by which they may be severally eliminated 

 from the system, the most important being the carbon dioxide, which is 

 discharged at the lungs, and the urea, which is excreted or thrown off by 

 the kidneys. 



The blood of the horse, like that of other mammals, is of a deep-red 

 colour, but brighter in the arteries than in the veins. The taste is mawkish, 

 the odour faint but peculiar, and its reaction to test-paper invariably alka- 

 line. Its specific gravity is about 1-061. It is clammy or slippery to 

 the touch, and is remark- 

 ably opaque, transmitting 

 but little light even in 

 thin layers. It is in con- 

 stant movement in the 

 body. The quantity of 

 the blood contained in a 

 horse of average size is 

 estimated to be about one- 



eighteenth 



I 



Fig. 184. Blood Corpuscles 



A, Coloured Blood Corpuscles adhering together in Columns 

 (rouleaux). B, Coloured Corpuscle, showing concave surface, 



c, The same seen edgewise. D, E, F, Colourless Corpuscles. 



of its body 

 weight, or from 40 to 

 45 Ibs., and it is con- 

 sidered that one-fourth is 

 contained in the heart and 

 larger blood-vessels, one- 

 fourth in the muscles, one-fourth in the liver and intestines, and the 

 remaining fourth in the other organs of the body. To the unassisted 

 eye, the blood as it issues from a wound appears to be perfectly homo- 

 geneous, but when examined with a microscope of moderate power it is 

 seen to be composed of a transparent fluid named the plasma, in which 

 are suspended a large number of corpuscles (fig. 184). The existence of 

 corpuscles in blood was first noticed in the hedgehog by the celebrated 

 Italian physician and anatomist Malpighi in the year 1661, who thought 

 they were globules of fat. They had previously been seen, in 1658, by 

 the Dutch anatomist Swammerdam in the frog, but this investigator lost 

 the credit of the discovery in consequence of his failing to publish his 

 observations. The real merit of recognizing the corpuscles as constant 

 and essential elements of the blood is due to another Dutch microscopist 

 named Leeuwenhoek, who in 1673 observed and described them in man 

 and many other animals. Great attention has been bestowed upon them 



