THE FLUIDS OF THE BODY 53 



of leucocytes. Removal of the tonsils is followed by no ill 

 effects. They are not essential to our well-being. Neverthe- 

 less, they have important functions to perform. They are 

 barracks crowded with leucocytes, which guard the pass into 

 the alimentary canal. Their leucocytes incessantly patrol the 

 mucous membrane, capturing germs, removing fragments of 

 injured epithelium, striving to make good the mischief to which 

 this part of the alimentary canal is peculiarly liable. The 

 enlargement of the tonsil which results from frequent sore 

 throat is a response to the demand for an increase in the 

 supply of these little scavengers, in order that they may cope, 

 not only with objectionable things outside the walls, but with 

 the still more pernicious germs which during an attack of sore 

 throat succeed in breaking through the epithelium. It is the 

 invaders which elude the vigilance of the leucocytes that cause 

 fever and other general symptoms. Other notable groups of 

 lymph-follicles are found in the middle portion of the small 

 intestine, where they form oval patches, about three-quarters 

 of an inch long by half an inch broad Peyer's patches. The 

 leucocytes which are developed in them search the walls of 

 the intestine for germs. During an attack of enteric fever 

 the patches become inflamed, and one of the greatest risks 

 which the patient runs is the risk of ulceration of a patch and 

 the perforation of the intestinal wall. 



The abundant provision for the multiplication of leucocytes 

 shows that the destruction of these cells must occur on an 

 equally large scale. Every day large numbers die. Where this 

 occurs, and how their dead bodies are removed, is not certainly 

 known. Doubtless they are eaten by their fellows, their sub- 

 stance oxidized, and the products carbonic acid, water, and 

 nitrogenous waste thrown into the lymph. There is some 

 reason for thinking that a part of the nitrogenous waste is 

 excreted in the form of uric acid (cf. p. 216). The daily pro- 

 duction, and consequent destruction, of leucocytes shows that 

 their metabolism is a factor which cannot be overlooked when 

 we are making up the body's accounts. 



The fixed tissues receive their nutriment in a digested con- 

 dition. Leucocytes digest it for themselves. In many cases, 

 although not in all, the cells of fixed tissues last throughout 

 life, so far as their outer form is concerned, although their 



