24 Dr Barclay -Smith, Extreme Visceral Dislocation. 



That profound changes do take place in the contents of the 

 csecum is a well-known fact, but little seems to be known as to 

 the character of these changes and the agents by which they are 

 brought about. As the large intestine seems to be the special 

 home of the intestinal bacteria, it is not too much to assume that 

 they are the principal digestive agents rather than a special in- 

 testinal secretion of which there seems to be no practical evidence. 



If bacteria play an important role in the digestive processes of 

 the herbivor, they have established a right to dwell as parasitic 

 inhabitants of the intestine, and there seems at first sight no 

 reason why they should not increase and multiply indefinitely, 

 and why the whole length of the intestine should not become 

 filled with a seething mass of bacterial colonies. 



Obviously it is a physiological necessity, in the first place, that 

 bacterial activity should be limited, and in the second place that 

 it should be localised. 



If the bacteria became too numerous and too active, the 

 breaking-down processes to which the food is subjected as the 

 result of their agency would become too profound, and no useful 

 purpose would be filled by their presence. Further, if there was 

 indefinite bacterial invasion of the small intestine, they would 

 seize upon and convert to their own use the material which was 

 the result of the normal digestive secretions. Being thus robbed 

 of valuable digested material, the animal might starve to death, 

 owing to the avidity of its guests. 



The means whereby bacterial activity is limited and localised 

 in the gut are probably two-fold. It is a well-known fact that 

 certain of the digestive fluids are inimical to bacterial life, bile 

 being a conspicuous example ; further certain decomposition pro- 

 ducts resulting from the digestion of food, such as the fatty acids, 

 must also have an important part to play in this respect. The 

 bactericidal influence of the intestinal contents, however, cannot 

 be the only means : if such were the case, the appearance of micro- 

 organisms in the intestinal tube would be a gradual and a varying 

 one ; whereas they do not make their appearance in any consider- 

 able quantity till the ileocolic valve is passed. 



The special restraining apparatus is probably furnished by the 

 collections of adenoid tissue which are such remarkable features in 

 certain parts of the intestine. 



Superficial masses of adenoid tissue typified by the tonsils, 

 have long been recognised as protective arrangements against 

 bacterial invasion, the tonsillar apparatus being regarded as more 

 especially protective to the air tube 1 . 



Agminated patches of adenoid tissue make their appearance 



1 Gulland, "Functions of Tonsils," Edinburgh MedicalJournal, 1891. 



