10 IMMUNITY IN HEALTH 



(5) That the lyrnphoid tissues of the tonsils and 

 appendix represent harriers protecting weak spots 

 against bacterial invasion. These regions are often ex- 

 posed to bacterial assault ; moreover, chronic bacterial 

 attacks in any part of the body lead tt) the accumula- 

 tion of lymphocytes and even the production of 

 lymphoid tissue. But the epithelium which is usually 

 a sufficient protection elsewhere also lines these regions. 

 Nor do sore throat's seem more common after complete 

 enucleation of the tonsils. Doubtless the full develop- 

 ment of these subepithelial lymphatic glands in the 

 individual is stimulated by bacteria, but the perpetua- 

 tion of the lymph nodes in the race is probably the 

 result of other functions of greater utility. 



(6) That the tonsils and appendix are purely mis- 

 chievous ^ acting as "portals of entry^^ and chronic 

 focuses of disease. In pathological circumstances they 

 do so act (Gouget, 1912), as indeed do other parts of 

 the body in diseased states. But this does not disprove 

 any useful function under physiological conditions. 



(7) That the tonsils and appendix produce lympho- 

 cytes, which pass into the lumen of the alimentary 

 tract and there keep down the numbers and restrain 

 the activities of the bacteria. Lymphocytes containing 

 ingested bacteria may be found in the mucus on 

 the surface of the tonsils, in the saliva and in the lumen 

 of the appendix. It is most likely also that the body in 

 some way, and to a certain extent, can control bac- 

 terial activity in the alimentary canal. Yet when one 

 considers the very small number of lymphocytes and 

 the myriads of bacteria, the conception is no longer 

 plausible. 



(8) That distension of the appendix initiates peri- 

 stalsis in the large ifitestine. To quote Adami and 

 McCrae (1914), '* The fluid contents of the ileum 

 pour into the caecum, and there and in the ascending 



