40 ORGANISED FLUIDS. 



of an inch. (See Plate I. fig. 6.) In the blood of reptiles, 

 especially in that of the frog, a contrary relation between the 

 size of the red and white globules exists ; the latter in these, 

 instead of being larger than the red corpuscles, are two or 

 even three times smaller. This fact it is important to bear 

 in mind in considering the question of the transformation of 

 the white globules into red. 



Form* Instead of being of a flattened and disc-like form, 

 as are the red globules, the shape of the white corpuscle, 

 when free, is in all classes of the animal kingdom globular. 

 This particular likewise throws much light upon the disputed 

 point as to whether the white globules become ultimately 

 converted into red corpuscles, and which we shall have to 

 treat of more fully hereafter. 



Like the red corpuscles, however, although to a less re- 

 markable extent, the white globules, when subject to pressure, 

 undergo a change of form : this change is frequently well 

 seen when viewing the circulation of the blood in the 

 capillaries, the white corpuscles often becoming compressed 

 between the walls of the vessels and the current of red blood 

 discs, and by which compression they are made to assume 

 elongated and oval forms ; like the red corpuscles, also, they 

 immediately regain their normal form, the pressure being 

 removed. 



Structure. In almost every relation which can be named, 

 the white globules would appear to be the antagonists of the 

 red ; for, instead of being of a homogeneous texture, they are 

 of a granular structure throughout, each full-sized white 

 globule being constituted of not less than from twenty to 

 thirty distinct granules, the presence of which imparts to it a 

 somewhat broken outline: these granules are often seen, 

 especially after the addition of water, and some other re- 

 agents, to be in a state of the greatest activity in the interior 

 of the corpuscles. It is only in the blood globule of mam- 

 malia, however, that we find this antagonism to prevail. 

 The blood corpuscle of the frog, and doubtless of other rep- 

 tiles, as well as birds and fishes, is assuredly a compound 

 structure, the investing or transparent part of each being in 



