50 BLOOD. 



or " dissolution." We have, as yet, no exact knowledge to guide us in the 

 matter, but we can readily imagine, that upon the death of the corpuscle, 

 the substances composing it, after undergoing changes, are dissolved by and 

 become part of the plasma. If so, the corpuscles, as they die, must repeat- 

 edly influence the composition and nature of the plasma. 



But if they thus affect the plasma in their death, it is even more probable 

 that they influence it during their life. Being alive, they must be continually 

 taking in and giving out. As we have already said, they are known to ingest, 

 after the fashion of an amoeba, solid particles of various kinds, such as fat 

 or carmine, present in the plasma, and probably digest such of these particles 

 as are nutritious. But if they ingest these solid matters they probably also 

 carry out the easier task of ingesting dissolved matters. If, however, they 

 thus take in, they must also give out; and thus by the removal on the one 

 hand of various substances from the plasma, and by the addition on the other 

 hand of others, they must be .continually influencing the plasma. We have 

 already said that the white corpuscles in shed blood as they die are supposed 

 to play an important part in the clotting of blood ; similarly they may dur- 

 ing their whole life be engaged in carrying out changes in the proteids of 

 the plasma which do not lead to clotting, but which prepare them for their 

 various uses in the body. 



Pathological facts aflbrd support to this view. The disease called leuco- 

 cythsemia (or leukaemia) is characterized by an increase of the white cor- 

 puscles, both absolute and relative to the red corpuscles, the increase, due 

 to an augmented production or possibly to a retarded destruction, being at 

 times so great as to give the blood a pinkish-gray appearance, like that of 

 blood mixed with pus. We accordingly find that in this disease the plasma 

 is in many ways profoundly affected and fails to nourish the tissues. As 

 a further illustration of the possible action of the white corpuscles we may 

 state that, according to some observers in certain diseases in which minute 

 organisms, such as bacteria, make their appearance in the blood, the white 

 corpuscles " take up " these bacteria into their substance, and thus probably, 

 by exerting an influence on them, modify the course of the disease of which 

 these organisms are the essential cause. 



If the white corpuscles are thus engaged during their life in carrying on 

 important labors, we may expect them to differ in appearance according to 

 their condition. Some of the corpuscles are spoken of as " faintly " or 

 " finely " granular. Other corpuscles are spoken of as " coarsely " granular, 

 their cell substance being loaded with conspicuously discrete granules. It 

 may be, of course, that there are two distinct kinds of corpuscles, having 

 different functions and possibly different origins and histories ; but since 

 intermediate forms are met with containing a few coarse granules only, it 

 is more probable that the one form is a phase of the other ; that a faintly 

 granular corpuscle, by taking in granules from without or by producing 

 granules within itself as products of its metabolism, may become a coarsely 

 granular corpuscle. 



Whether, however, the white corpuscles are really all of one kind, or 

 whether they are different kinds performing different functions, must at 

 present be left an open question. 



Blood Platelets. 



33. In a drop of blood examined with care immediately after removal 

 may be seen a number of exceedingly small bodies (2// to 3/Jt in diameter), 

 frequently disc-shaped, but sometimes of a rounded or irregular form, homo- 

 geneous in appearance when quite fresh, but apt to assume a faintly gran- 



