158 ORIGIN OF NATURAL IMMUNITY, 



the presence of a foreign cell (microbe) and secrete immunity 

 bodies that dissolve the intruder, it must not be forgotten that 

 the microbe Avill in turn secrete anti-bodies which will annul the 

 action of the immunity bodies. Welch | pointed this out, but why 

 did he stop at the response of the microbic cell ? The body cells 

 will respond to the microbic anti-body, and so the production of 

 enzymes and anti-enzymes, toxines and anti-toxines, will go on 

 until the microbe or the animal is overcome. The digestion of 

 bacteria may take place in the body fluids or in the bod}^ cells 

 and tissues, which, it must not be forgotten, are saturated with 

 the same fluids and contain the same digestive enz3^mes, if the 

 latter are diftusible. That some of them are difl'usible is shown 

 by the bacteriolytic power of the fluids. It is inconceivable that 

 immunity bodies can be generated in the fluids themselves. The 

 constituents of these fluids must be produced and be contained in 

 and be excreted or secreted b}^ the wandering and fixed body 

 cells, the plasma of which will be saturated. Digestion will, 

 therefore, be more rapid when the micro-organism is within the 

 body cell, and especially is this the case if the enzyme is feebly 

 diffusible or non-diffusible. In the event of a bacterium 

 getting into the bod}^ fluids it will be attacked by the enzymes of 

 that fluid, and by the nearest cells which will also respond to the 

 stimulus and secrete more. The cells which come into action are 

 and must be the most mobile ones, for they get nearer to the 

 intruders than the others; distance must be of great moment in 

 supplying the stimulus. It would be foolish to expect that the 

 cells of the ear would respond to the presence of an organism in 

 the toe. It is because of the mobility of the leucocytes that we 

 have the idea that they are chiefly responsible for the production 

 of the immune digestive enzymes. 



The inclusion or swallowing of the microbe by the leucocyte is 

 not, strictly speaking, an immunity phenomenon, for any amoeboid 

 cell will surround and enclose any digestible or slowly soluble 



: Brit. Med. Journ. Oct. 11th, 1902, p. 1109. 



