OTHER MICROSCOPIC ELEMENTS IN BLOOD. 



215 



protoplasm a number of red corpuscles, or in some cases partially disintegrated portions of red 

 corpuscles. The white corpuscles also tend to take into their protoplasm bacteria and other 

 micro-organisms, which, according to Metschnikoff , may become destroyed within the corpuscles. 

 They also appear to play an important part in absorption of solid and fatty particles, both from 



Fig. 250. COLOURLESS CORPUSCLES TREATED WITH 



WATER AND WITH ACETIC ACID (E. A. S.). 



1, first effect of the action of water upon a white 

 blood-corpuscle ; 2, 3, white corpuscles treated with 

 dilute acetic acid ; n. nucleus. 



the intestines and in the physiological and pathological absorption of the tissues (absorption of 

 tadpole's tail, formation of abscesses). Leucocytes which have thus "devoured " other cells or 

 foreign substances are often termed phagocytes. They are often of large size, but it has not 

 been shown that they are morphologically different from ordinary white blood- corpuscles. 



Other microscopic elements in blood. In the clear fluid which intervenes 

 between the corpuscles, and which, in a preparation which has been made a short 

 time, consists of serum, there can generally be 

 detected a network of fine interlacing filaments of 

 fibrin (fig. 251). There are also to be seen minute 

 round colourless discoid particles in this fluid, which 

 are usually massed together into groups, containing 

 from a very few to an immense number of particles. 

 They were first described under the name of elemen- 

 tary particles by Zimmermann, and attention was 

 subsequently drawn to them by Hayem, who re- 

 described them under the name " haematoblasts " as 

 a source whence new red corpuscles are derived. 

 Still more recently these structures have been again 

 investigated by Bizzozero, who has termed them " blood-platelets," and has ascribed 



Fig. 251. NETWORK OF FIBRIN, SHOWN 



AFTER WASHING AWAY THE COR- 

 PUSCLES FROM A PREPARATION OF 

 BLOOD THAT HAS BEEN ALLOWED 

 TO CLOT. (E. A. S.) 



Many of the filaments radiate from 

 small clumps of blood-tablets. 



(f 



* 



'iwpjt 



Fig. 252. MASS OF BLOOD-PLATELETS, SHOWING THE CHANGES WHICH IT UNDERGOES AT ITS PERIPHERY 



WHEN OBSERVED IN SALT SOLUTION ON THE WARM STAGE. (Osier.) 



to them special functions not only in connexion with the regeneration of the red 

 corpuscles but also with the formation of fibrin-ferment. 



It is certain that they are much more numerous 

 in disease and especially in cachectic states of the 

 system than in the normal condition, but they 

 appear to be never altogether absent even in per- 

 fectly healthy blood. Lowit believes that the plate- 

 lets are nothing but particles of globulin which have 

 become precipitated from the plasma after the blood 

 has been drawn, and others have thought that they 

 are produced by the solution of some of the pale cor- 

 puscles, but for both these views there appears to be 



insufficient evidence. It was shown by Osier that they occur free within the 

 blood-vessels (fig. 253), although they become massed together immediately the blood 

 is drawn. The fibrin-filaments which then form, almost invariably radiate from 



Fig. 253. BLOOD - CORPUSCLES AND 



PLATELETS WITHIN A SMALL 

 VEIN OF THE RAT's MESENTERY. 



(Osier.) 



