EXPLANATION OF PLATES 



Plate I 



Fig. 1. B. acidophilus. Stained preparation from culture in glucose broth 

 incubated forty-eight hours at 37° C. Note the pleomorphism of the organ- 

 ism. X 1000. 



Fig. 2. B. bulgaricus. Stained preparation from pure culture in whey 

 broth incubated forty-eight hours at 37" C. Note close similarity of the 

 individual cells and chains of this and the preceding figure. X 1 000. 



Plate II 



Fig. 3. Forty-eight-hour colony of B. acidophilus on glucose agar incu- 

 bated at 37° C. X 100. 



Fig. 4. Forty-eight-hour colony of B. bulgaricus on whey agar incubated 

 at 37° C. X 100. Note the similarity of the two colonies. 



Plate III 



Fig. 5. Surface growth of B. acidophilus in a tube of whey agar grown 

 aerobically at 37° C. for forty-eight hours. Note small discrete colonies. 

 X4. 



Plate IV 



Fig. 6. Colonies on whey agar plates prepared from feces of human 

 subject immediately preceding a period during which 1000 cc. of B. acidoph- 

 ilus milk was taken daily. Note absence of small irregular and fluffy 

 colonies. X 40. 



Fig. 7. Colonies on whey agar plates prepared from feces during the 

 period in which 1000 cc. of B. acidophilus milk were taken daily. Note the 

 dominating colonies of B. acidophilus which are characterized by their small 

 size and very irregular border. X 40. 



Plate V 



Fig. 8. Veillon tubes used in the present investigation, demonstrating 

 their particular value in the determination of gas-producing organisms in 

 the intestine of the white rat and of man. Note the gradual diminution of 

 gas production from left to right in the series of six tubes. The gradations 

 correspond to the different stages of transformation of the usual complex 

 flora to the simple flora dominated by B. acidophilus. Natural size. 



