The Blood. 35 



Pas consists largely of white cells collected in the tissues 

 and forming an abscess. 



No doubt many corpuscles leave the blood the destruc- 

 tion of which we are unable to account for, but it is pro- 

 bable, as suggested by Michael Foster, that by their death 

 they influence the composition of the blood plasma, as in 

 this fluid their component parts must become dissolved 

 after their death. 



During the life of the white corpuscle great activity pre- 

 vails, it is constantly giving up and taking in material 

 which must affect the composition of the plasma. We 

 know that the white cell possesses the power of digesting 

 certain substances, both solid and liquid. The researches 

 of Metschnikoff have paved the way towards a better 

 understanding of the probable way in which protection 

 against certain diseases is obtained. The white cells 

 digest the bacteria, taking them up into their own sub- 

 stance ; it is a fight between bacteria and leucocytes ; the 

 protection afforded to the system by the white blood-cells 

 is therefore not the least important of the functions per- 

 formed by them. 



On the death of the blood the white cells yield the so-called 

 fibrin ferment, which produces the clotting of the blood. 



A Third Corpuscle is described as found in the blood, 

 termed by Hayem Haematoblast, and by Bizzozero Blood- 

 plate. Their function and nature is unknown, though 

 according to some they take an active part in that obscure 

 process the clotting of the blood. Blood-plates are found 

 in large numbers in the white thrombi found in vessels, 

 and they may be readily obtained by passing a thread 

 through a blood-vessel, or suspending threads in freshly- 

 drawn blood (Bizzozero, Stirling). Semmer calls these 

 plates red granular corpuscles ; he states that they exhibit 

 amoeboid movement, and has examined them in the blood of 

 the horse and other animals (Gamgee). 



Coagulation. — We are now brought to a consideration of 

 the subject of blood clotting, a process by which the 

 naturally fluid blood becomes converted into a solid. 



3—2 



