86 APPLIED PHYSIOLOGY 



actually to destroy living organisms, and they were 

 degraded from the rank of ' soldiers ' to that of a set 

 of mere ' scavengers ' or ' undertakers ' who removed 

 from the field of action the bodies of micro-organisms 

 already killed by the blood or tissues. At the present 

 time the very important part played by the leucocytes 

 in the destruction of bacteria is generally admitted, 

 though it is now recognized that many fixed cells of 

 the body (e.g., endothelial cells and connective-tissue 

 corpuscles) have a similar property. Nor are all forms 

 of leucocytes to be regarded as phagocytic. The lympho- 

 cytes, the eosinophils, and the mast cells are not so 

 endowed. In addition to these duties, it must be remem- 

 bered that leucocytes produce ferments e.g., fibrin 

 ferment, and possibly fat-splitting and tryptic ferments 

 as well. They also play an important part in the repair 

 of the body after injuries. 



The abundance of lymphocytes in the neighbourhood 

 of the alimentary canal would lead one to suppose that 

 they may have some part to play in nutrition, possibly 

 in the absorption of proteins or in the carriage of fat or 

 glycogen. The greater number of lymphocytes in the 

 blood during the earliest years of life would also seem 

 to indicate that they may have nutritive functions. On 

 the other hand, they are increased like other white cells 

 in the neighbourhood of infections, and there is reason 

 to believe that in the lymph glands they inhibit the 

 growth of bacteria, although incapable of ' englobing ' 

 them. It is thus possible that the lymphocytes aid in 

 the protection of the body. 



The functions of the eosinophils are even less under- 



