BLOOD-CORPUSCLES. 



FIG. 1. Human blood-corpuscles ; magnified 370 diam- 

 eters. (From a photograph taken at the United States 

 Army Medical Museum.) 



of blood, and, according to the observations of all who have investigated this subject, are 

 more abundant in the male than in the female. 



The form of the blood -corpuscles is peculiar. They are flattened, biconcave, circular 

 disks, with a thickness of from one-fourth to one-third of their diameter. Their edges 

 are rounded, and the thin, central portion 

 occupies about one-half of their diameter. 

 Their consistence is not much greater than 

 that of the plasma. They are very elastic, 

 and, if deformed by pressure, immediately 

 resume their original shape when the press- 

 ure is removed. Their specific gravity is 

 from 1088 to 1105, considerably greater 

 than the specific gravity of the plasma, 

 which is about 1028. (Robin.) 



When the blood has been drawn from 

 the vessels and coagulates slowly, the great- 

 er density of the red corpuscles causes them 

 to gravitate to the lower portions of the 

 clot, leaving the white corpuscles and fibrin 

 at the surface. This is the cause of the 

 "buffy-coat" mentioned by some writers. 

 If coagulation be prevented by the addition 

 of a small quantity of sulphate of soda, 

 there is quite a marked gravitation of red corpuscles after standing for some hours. 



The peculiar form of the blood-corpuscles gives them a very characteristic appearance 

 under the microscope. Examined with a magnifying power of from three hundred to five 

 hundred diameters, those which present their flat surfaces have a shaded centre when the 

 edges are exactly in focus. This appearance was formerly supposed to indicate the ex- 

 istence of a nucleus having a constitution different from that of the rest of the corpuscle. 

 It is now understood to be an optical effect, the result of the form of the corpuscles ; their 

 biconcavity rendering it impossible for the centre and edges to be exactly in focus at the 

 same instant, so that, when the edges are in focus, the centre is dark, and, when the cenr 

 tre is bright, the edges are shaded. 



As the blood-corpuscles are examined 

 by the microscope by transmitted light, 

 they are nearly transparent and of a pale- 

 amber color. It is only when they are col- 

 lected in masses that they present the red 

 tint characteristic of blood as it appears 

 to the naked eye. This yellow or amber 

 tint is quite characteristic. A pretty good 

 idea of the color may be obtained by large- 

 ly diluting blood in a test-tube and holding 

 it between the eye and the light. 



In examining blood under the micro- 

 scope, the corpuscles are seen in many 

 different positions ; some flat r some on 

 their edges, etc. This assists us in recog- 

 nizing their peculiar form. 



FIG. 2. Human red blood-corpuscles, arranged in rows, 

 with two white corpuscles, or leucocytes. 



It has long been observed that the blood- 

 corpuscles have a remarkable tendency to 

 arrange themselves in rows like rouleaux of coin. This appearance has attracted univer- 

 sal attention, and for a long time it was not satisfactorily explained. Robin, however, has 



