BACTERIOLOGY OF THE OYSTER. 49 



From the table it is seen that in only two oysters, numbers six and 

 eleven, out of the forty-one examined, was the number of bacteria 

 per unit volume greater in the stomach contents than in the shell 

 liquor. In oyster, twenty-eight the numbers were equal. In the 

 remaining thirty-eight oysters there were more bacteria per unit 

 volume in the shell liquor than in the stomach contents. In these 

 thirty-eight oysters the ratio per unit quantity of the number of 

 bacteria in the shell liquor to the number in the contents of the 

 stomach varied from 3 to 2 in oyster Nos. 37 to 2000 to 1 in oyster 

 No. 41. The ratio of the total numl^er of bacteria per unit volume 

 in the shell liquor of the forty-one oysters to the total number of 

 bacteria in an equal quantity of the stomach contents was as 21.6 to 1. 

 That is, a comparison of the average number of bacteria found in shell 

 liquor with the number of bacteria in the stomach contents shows that 

 per unit quantity there were more than twenty times as many bacteria 

 in the shell liquor as in the stomach juice. 



LENGTH OF TIME NECESSARY FOR BACTERIA TO PASS 

 THROUGH THE INTESTINAL TRACT OF THE OYSTER. 



So far as the writer is aware no one has ever made any determination 

 of the rate at which food passess through the alimentary tract of the 

 oyster. While it is difficult to determine this matter directly, it 

 seemed possible to inoculate the shell liquor of oysters with some 

 bacterium not found in oysters and trace its progress through the 

 intestinal canal. B. prodigiosus was chosen because of its ease of 

 identification and because the writer has never found it in oysters, 

 and so far as he is aware it has never been reported as occurring in 

 oysters. 



In the first experiment twelve oysters were inoculated by sawing off 

 a piece of the lip of the shell and inserting a loopful of a culture of B. 

 prodigiosus into the branchial chamber. The oysters were layed very 

 carefully upon cotton tiioroughly saturated with water and covered 

 wdth a glass dish to prevent evaporation. They were kept at the 

 laboratory temperature which is about 20°C. At various intervals, 

 as shown in the tables, three oysters were removed and examined. The 

 examination was made as follows: — The right valve of the oyster 

 was removed and the gills and mantle carefully dissected away. The 

 remaining part of the body was then washed for several minutes in 

 running tap water. The left valve containing the oyster was then 



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