THE BLOOD AND THE LYMPH. 705 



V 



are consequently vesicles, whence the name " blood-cells" is to be pre- 

 ferred. The elasticity, softness, and flexibility of the membrane is so 

 considerable, that the corpuscles are rendered capable of passing through 

 vessels of less diameter than themselves, and when by pressure under 

 the microscope they have become elongated, flattened, or otherwise 

 altered in shape, of reassuming their original form. The blood-globules 

 are the better adapted for the former process, since their surface is per- 

 fectly smooth and slippery, so that they easily glide over the walls even 

 of the smallest capillaries, which present the same conditions. 



The size of the blood-globules may differ in different individuals ; but 

 these diversities, owing to the minuteness of the bodies concerned, are 

 not altogether inconsiderable. As a general mean size, the most recent 

 inquiries of Harting (" Rech. micrometr.") from measurements of recent 

 blood-corpuscles, give a width of 0-0033 (1-300) and a thickness of 

 0*00062 of a line ; and of Schmidt, from the estimation of dried blood- 

 globules, a width of 0*0035 of a line, whilst, according to the former, 

 the mean width in various individuals amounts to from 0-0028 to 

 0-0036, and according to Schmidt to 0-0032-0-0035 of a line, with 

 which numbers those given by other good observers essentially corre- 

 spond. The differences in the same individual, found by Harting to exist 

 between the two extremes, amount, as regards the width, to 0-0010- 

 0-0017, and for the thickness to 0-00009-0-0005 of a line; the ex- 

 tremes observed in general were 0-0020-0-0040 and 0-0005-0-0009 

 of a line ; and Schmidt states, that in 100 blood-corpuscles 95-98 are 

 of equal size. With respect to the size of the blood-globules in one and 

 the same individual, it may be stated in general, that it necessarily 

 differs at different times, and especially that it necessarily increases or 

 diminishes according to the varying degrees of concentration of the 

 blood-plasma ; but on this subject we have scarcely any accurate re- 

 searches. Harting only says, that the blood-corpuscles of the same in- 

 dividual, measured after an interval of three years, presented the same 

 mean size, whilst in the same individual after a copious meal, somewhat 

 less average dimensions were exhibited (by about 0-00013 of a line), and 

 more considerable extremes. It has been remarked that determinate 

 data are wholly wanting as to the number of the blood-globules, and we 

 must await the results of Vierordt's researches. But, at all events, from 

 what has been ascertained with respect to the amount of solid constitu- 

 ents in the blood-globules, this much in general may be concluded, that 

 they are more numerous in the male than in the female sex ; moreover, 

 that after repeated venesection, during pregnancy and after prolonged 

 deprivation of food, they dimmish in number; and in certain diseases, 

 as chlorosis and ancemia, are also found to be much more scanty than 

 usual. At the same time, however, it is certain, that all the possible 

 variations are not as yet by any means exhausted, and it can scarely be 



45 



