78 



and in addition two stray, not typhoid, colonies : one on the 

 left middle, one near the upper left part of margin. The sea 

 water therefore contained 13,180 B. typhosus per 1 c.c. 



SERIES II. 



Figs. 1, 2, 3, and 4 represent plates made from wet oysters 

 of same lot as Experiment IV. 



Fig. 1. Oyster 1, kept for 24 hours in typhoid-infected 

 water the plate was made with T J-0 part of the oyster ; it 

 yielded 958 blue colonies of B. typhosus, and 9 colonies of 

 B. coli communis, seen in the photo as large, white, opaque 

 colonies. There were in addition three or four other non- 

 descript colonies ; the above result would amount to 95,800 

 B. typhosus and 900 B. coli communis per oyster. 



Fig. 2. From same lot, oyster 3, 24 hours in typhoid- 

 infected water, two days afterwards in sterile water ; T J - part 

 of the oyster yielded 7520 blue colonies of B. typhosus, 

 calculated by counting as carefully as possible two separate 

 -^ sections of the plate ; there were no colonies of B. coli in 

 the plate. This would mean 752,000 B. typhosus per oyster. 



Fig. 3. From same lot, oyster 5, 24 hours in typhoid-in- 

 fected water, four days afterwards in sterile water ; T J- - part of 

 the oyster was used for the plate ; it yielded 12 (blue) colonies 

 of B. typhosus, three large and ten minute neutral nondescript 

 colonies. This would mean 1200 B. typhosus per oyster. 



Fig. 4. From same lot, oyster 9, 24 hours in typhoid- 

 infected water, seven days afterwards in sterile sea water; 

 J part of the oyster yielded 63 (blue) colonies of B. typhosus. 

 This amounts to 378 B. typhosus per oyster. 



SERIES III. 



Figs. 1, 2, and 3 represent plates made from oysters of 

 dry lot, of same Experiment IV. 



Fig. 1. Oyster 2, 24 hours in typhoid-infected water, 

 and two days afterwards kept dry ; jfa part of the oyster 



