SEA-FISHERIES LABORATORY. 133 



The percentages for the fourth experiment cannot be 

 given since the mode of reduction is not quite the same as 

 in the first three experiments. The numbers of bacteria rise 

 from the first to the second days and then fall, and after 

 this initial rise the mode of diminution is the same as in the 

 earlier experiments. The difference is due to the fact that 

 a certain quantity of food-medium was added with the bacilli 

 inoculated, so that an initial multiplication took place. After- 

 wards, however, the same manner of fall is to be seen from 

 the figures. 



The graphs of these three experiments are rectangular 

 hyperbolas, and are : — 



I. yx 241 = constant. 



II. yx 8 - 1 = constant. 



III. yx 5 - 5i = constant. 



The index of x, that is, the slope of the curve, the measure 

 of the rate at which the bacteria die off during the experiment, 

 is greatest in I and least in III. This means that the successive 

 cultivation of the same strain through sea-water has affected 

 the organisms, so that their resistant power to the change 

 medium has become less in the course of each experiment. 

 The constant, of course, only affects the scale to which the 

 results are plotted, or otherwise expressed. 



(3) The disappearance of intestinal bacteria from Mussels 

 subjected to a cleansing process. 



It has been known for some time that intestinal bacteria 

 disappear from shellfish allowed to stand in still, or running 

 sea-water. The first experiments of this kind were made by 

 Klein at St. Bartholomew's Hospital as long ago as 1905. 

 Oysters, mussels and cockles were dosed with enormous 

 quantities of typhoid bacilli, and allowed to stand in wooden 

 tubs containing sterile sea-water. After several days a very 

 marked diminution in the numbers of the contained bacilli 



