32 HISTORY OF THE CORPUSCLES. [BOOK i. 



transformed into the red corpuscle ; if this is the case the keeping 

 up a supply of red corpuscles cannot, as was once thought, be an 

 important end of the existence of white corpuscles in general. We 

 have already (p. 22) dwelt on the probability that the coagulation 

 of shed-blood is due to white corpuscles breaking up and discharg- 

 ing certain fibrin-factors into the plasma ; but it is uncertain in 

 the first place whether this function is to be attributed to all white 

 corpuscles or to a special kind only, and in the second place 

 whether in normal conditions of the economy any appreciable 

 amount of fibrin-factors are in this way habitually discharged into 

 the blood, and as constantly got rid of without fibrin being formed. 

 It is quite possible that normal circulating plasma may always 

 contain a certain stock for instance of fibrinogen, which is 

 continually being drawn upon for the nourishment of the tissues, 

 and as continually replaced by the destruction of corpuscles. But 

 there are no facts at present which absolutely contradict the view 

 that fibrinogen is normally absent from intact circulating plasma, 

 and that the arrangements for the manufacture of fibrin exist only 

 for the purpose of meeting the contingency of fibrin being required 

 under circumstances which may be considered abnormal. 



On the other hand we know that in an inflamed area the white 

 corpuscles migrate in large numbers into the extravascular portions 

 of the tissues, and it has been maintained that not only the pus 

 corpuscles and ' exudation' corpuscles which are the common pro- 

 ducts of inflammation, but even the new tissue elements (connec- 

 tive-tissue cells and fibres), which make their appearance as the 

 result of the so-called 'productive' inflammations, are the descen- 

 dants, immediate, or remote, of such migratory corpuscles. But 

 a discussion of this question would lead us too far away from the 

 purpose of this work. 



It would appear therefore that with the exception of the respira- 

 tory function of the red corpuscles, the physiological interest of the 

 blood is attached rather to the plasma than to the corpuscles. 

 \ II The work, done by the corpuscles, even when it is fully under- 

 , \ stood, will, with the exception of the carrying of oxygen by the 

 red corpuscles, always appear insignificant compared with the 

 incessant labours of the plasma, which is for ever busy as the 

 middle-man between the several tissues, bringing to each tissue 

 what it needs and taking from it that which is useless or even 

 injurious to itself but necessary to the well-being of some other 

 part. 



