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The Alimeniary Canal as a Source of Contagion. 



The mucous membrane of the alimentary canal is pre-eminently an 

 absorbent surface. It is constantly bathed in liquid swarming with 

 bacteria, and yet only in rare instances apparently do these bacteria 

 pass through its walls to gain entrance to the blood- and lymph-circula- 

 tions. The great mass of them, many varieties being highly toxic, is 

 rejected by the absorbents, and so, under natural circumstances, the 

 blood remains free from contamination. 



The cause of this cannot reside in the presence of a defensive barrier 

 of phagocytes in the intestinal wall, for no such barrier has ever been 

 demonstrated, and, moreover, it would be hard to suppose that any such 

 means of protection would be sufficient to deal with the enormous 

 numbers of bacteria of different kinds constantly passing along the 

 intestinal channel. 



Certain bacteria, as for example that of typhoid or of tubercle, do 

 become absorbed, make their way into particular organs, and germinate 

 upon them, while the numerous other organisms lying in their vicinity 

 fail to be absorbed, or, if absorbed in small quantity, are destroyed 

 by the blood or lymph. 



How this is effected, and why there should be such a selective 

 affinity in favour of one organism, is as yet shrouded in obscurity, 

 although manifestly the function, whatever it may depend upon, must 

 play an all important role in protecting the body under conditions of 

 health from bacterial invasion. 



Comparative Study of Certain Contagious Diseases 

 of the Sheep. 



The subject, it will be confessed, is one of intense interest, and 

 my attention has been directed to it by the study of a remarkable class 



(3) BI 



