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Firstly, there is a digestive leucocytosis. It is found that, 

 as a rule, within one hour of a meal, more especially a meat 

 meal, the number of leucocytes begins to increase. This 

 continues for several hours, reaches its maximum in three or 

 four hours, and then gradually declines. 



This leucocytosis rarely reaches a higher figure than 15,000 

 or 16,000 per cubic millimetre. 



In its character it is a mixed leucocytosis. Both the 

 lymphocytes and the polynuclear cells are increased, more 

 especially the lymphocytes. 



The explanation of this phenomenon is that, with the 

 process of digestion the lymph tissues of the intestinal tract, 

 and they are extensive, become stimulated, and a raised lymph 

 circulation occurs. " In consequence of this increased flow 

 more elements are mechanically washed out of the lymph 

 glands." 



The increase of the polynuclears, on the other hand, is 

 due to a positive chemiotaxis, the assimilated products of 

 metabolism, stimulate the marrow and cause an outpouring of 

 the polynuclear cells into the blood stream. 



I need only mention in passing a few other well-organised 

 forms of physiological leucocytes, for example that occurring 

 during the later months of pregnancy and that found during the 

 first year of life. In neither is the leucocytosis at all marked. 

 A leucocytosis is also found to occur after bodily exertion and 

 following cold baths. 



Apart from these few exceptions leucocytosis is an 

 abnormal condition, and as previously suggested is probably of 

 the nature of a protective reflex. 



Two forms are described — (1) A passive leucocytosis, in 

 which the cells are simply washed- into the blood stream by 

 mechanical forces. Of this class are the different kinds of 

 lymphocytosis. 



In direct contrast there is the " active leucocytosis," in 

 which the cells involved are capable of spontaneous movement 

 and activity, and emigrate into the blood in response to a 

 stimulus. 



