196 INFECTIONS OF THE DIGESTIVE TRACT 



teeth in caries to be infiltrated by this organism appar- 

 ently in almost pure culture. Moreover, he has been able 

 to induce a putrefactive decomposition in the substance 

 of teeth previously decalcified by the use of acid. While 

 the evidence thus far brought forward in regard to the 

 role of B. putrificus in causing disease of the teeth is not 

 complete (owing to the difficulty in excluding some 

 symbiotic action of other kinds of bacteria), it appears 

 in the highest degree probable that B. putrificus is 

 an important factor in setting up caries. As this 

 organism is an anaerobe, it is easy to see how scrupulous 

 cleanliness of the teeth and gums must operate to pre- 

 vent it from gaining a foothold in the mouth. 



Bacillus aerogenes capsulatus. B. aerogenes cap- 

 sulatus is a strictly anaerobic, difficultly spore-bearing, 

 Gram-positive, gas-making bacillus. It is found in 

 small numbers relatively to other bacteria in the intes- 

 tines of the majority of normal adults and in still smaller 

 numbers in normal children. There are many healthy 

 breast-fed and bottle-fed children hi whom one fails 

 to find evidence of the presence of this microorganism 

 in the intestinal tract, either through careful study of 

 the Gram-stained microscopical faecal field or through 

 ordinary plating methods. I will not say that the organ- 

 ism is actually absent from the intestine in these cases, 

 but it is certain that if present it is in such small numbers 

 as to play no appreciable part in the biochemical pro- 

 cesses that occur in the digestive tract. Our knowledge 

 of the part played by this anaerobe in human pathol- 

 ogy has until very recently been limited to certain 



