THE BLOOD. 113 



comprehends all the liquid part in the physiological system. 

 These two parts are in equal quantities, and we may thus 

 define the blood as a certain mass of cruor, floating in a 

 quantity of liquor of equal bulk. 



Yet this proportion may vary, particularly in the cases 

 already mentioned. During the process of absorption the mass 

 of blood may be doubled ; it is the liquor especially which then 

 increases, and this increase is due to the large quantity of 

 lymph which is poured into the circulating current. (Colin 

 collected from a cow, by means of a fistula in the thoracic 

 duct, as much as ninety-five litres of lymph in twenty-four 

 hours.) After copious bleeding also, the blood has a tendency 

 to recover its former bulk by borrowing fluid constituents 

 from the adjacent tissues ; the quantity of liquor will then 

 be increased, the process being much slower in regard to the 

 cruor. We know, too, that death generally ensues when 

 half the blood has been drained away by hemorrhage, or 

 rather, to speak correctly, when half the cruor has been 

 withdrawn, the importance of which fact is evident in the 

 case of successive bleedings ; because the liquid part of the 

 blood, and not the globules, has had time to be re-formed. 



Cruor. This is the solid part of the blood, and is formed 

 entirely of globules, floating in liquid : the blood globules are 

 of two kinds, red and white. 



a. The white globules of the blood, better named colorless 

 globules (Leucocytes, Robin), are a little larger than the red 

 (from eight to nine thousandths of a millimetre in diameter), 

 but much less numerous (there is, in general, one white to three 

 hundred red globules) ;-they are spherical in shape, and sim- 

 ilar in every respect to the lymph globules which are found 

 in the lymphatic glands: they originate, in fact, in these 

 glands, and are subsequently detached from them, and drawn 

 by the lymph into the thoracic duct, whence they spread, 

 with the lymph, throughout the blood. These globules are 

 round, having nuclei, and a slightly granular surface (Fig. 

 31). When examined in the liquor of the blood, with a 

 magnifying power of from 200 to 300 diam., they seem to 

 have a granular appearance and are irregular in shape, their 

 color being a peculiar silvery white. Under these circum- 

 stances it is impossible to distinguish any other details of 

 their structure ; but, on the addition of water, we find that 

 these elements increase in size, their outline becomes smooth, 

 and a nucleus appears, sometimes double or multiple ; the 

 addition of acetic acid renders these features still more dis- 



