CHAP. XXVII.] THE BLOOD-CORPUSCLES. 297 



improbable that they may be constantly being developed by the 

 chemical changes which are unceasingly going on in that fluid, but 

 that they become attracted from it as quickly as they are formed in 

 it, and do not accumulate in it in any quantity which admits of being 

 easily detected. According to Dr. Thomson, sugar may be always 

 easily detected in the blood, shortly after a meal containing starch.* 



The Fibrine. We have already explained the manner in which 

 fibrine may be obtained from the blood. One thousand parts of 

 healthy blood contain two or three of fibrine. A pint of blood will 

 therefore yield about twenty-nine grains of fibrine, adopting the 

 highest estimate. 



Pure fibrine, or, to speak more exactly, fibrine separated from 

 the red corpuscles, for it cannot be completely separated from the 

 colourless corpuscles, has a remarkable tendency to assume the 

 fibrous form. A drop of the colourless liquor sanguinis, which 

 is found on the surface of blood, about to form a bufiy coat, 

 exhibits, when coagulated, an intricate interlacement of minute 

 fibres. Here and there a colourless cell is entangled in it, ap- 

 pearing as a centre, whence pass numerous radiations of minute 

 fibres. Dr. W. Addison, who believes that the fibrine is contained 

 within the colourless corpuscles, considers the bursting of a large 

 number of these, and the consequent liberation of their enclosed 

 fibrine, as the first step in the process of coagulation, which 

 explains the entanglement of them in the fibrillating fibrine. The 

 process may be best seen, as this excellent observer recommends, 

 by examining a drop of the colourless liquor sanguinis from blood, 

 about to form a bufiy coat, and allowed to coagulate upon a slip 

 of glass.f 



The Red Corpuscles. It is to the multitude of coloured particles 

 which float in the liquor sanguinis, under the name of " the red 

 corpuscles," that the blood owes its colour. To examine these, it 

 is only necessary to place a drop of blood in the field of the 

 microscope, taking care to dilute it with a fluid, similar or nearly 

 so in specific gravity to the serum : a solution of sugar or of salt 

 in water, answers this purpose completely. So numerous and 

 so crowded together are the corpuscles in a drop of blood, that 

 it would be difficult to obtain a complete view of any one of them 

 without this precaution. 



In the human blood, the coloured corpuscle is a circular double 

 concave lens ; from being concave on each surface, its margin is 

 thick and rounded, and its thickness is less in its centre than at 

 * LOG. cit, t Dr. W. Addison's second series of Exp. Kesearches, 1843. 



VOL. II. X 



