CHAPTER VI. 



Alimentary Immunity, 



And it is proposed to argue that not only have these 

 glands a prophylactic tendency against infectious 

 disease such as scarlatina, measles, variola, diphtheria, 

 whooping cough, influenza, acute anterior poliomye- 

 litis, epidemic cerebro-spinal meningitis, rheumatic 

 fever and typhoid fever ; but also that to these glands 

 man owes his protection against most of the bacteria 

 in his alimentary canal. The high degree of tolerance 

 that man displays towards the teeming denizens of 

 his intestines has often been noted as a remarkable fact. 

 Streptococci, pneurhococci and diphtheroid bacilli are 

 almost constantly present in the throat ; coli bacilli 

 swarm in the intestines ; one half of the w^eight of the 

 faeces is contributed by the bodies of micro-organisms 

 (Starling, 1912). All these, it will be here alleged are 

 rendered impotent for evil at least partly because the 

 body is forewarned and forearmed by its outpost forts 

 of lymphoid tissue. Of course, the living epithelium 

 of the alimentary tract is in itself a formidable barrier. 

 But when that is passed the body is still capable of 

 disposing of considerable numbers of intestinal bac- 

 teria, unless it is hindered by mechanical or chemical 

 irritation. Many a surgeon has marvelled at the bac- 

 tericidal powers of the peritoneum in cases of wounded 



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