49 



It appears then, from this series, that the cockles embody 

 readily a large number of the B. typhosus from the infected 

 sea water, larger in proportion than oysters. In Experiment 

 II, after 24 hours in infected water, the proportion of B. 

 typhosus in the oyster and 1 c.c. of sea water was as 40 to 

 744 (or about 1 : 18) ; in Experiment III it was as 84 to 

 2250 (or about 1 : 26) ; in Experiment IV it was as 95 to 

 2470 (or 1 : 28) whereas in the case of the cockles of Ex- 

 periment V it was as 500 to 4000 or 1 : 8. 



Another striking fact is the persistence of B. typhosus in 

 large numbers in the cockles even after ten days' change; 

 24 hours after infection the cockle examined had half a 

 million ; after ten days the normal cockle 14a still contained 

 69,000 B. typhosus. 



The abnormal cockle, on the other hand, had a greatly 

 reduced number, viz., 1600 B. typhosus, so that as compared 

 with the abnormal oyster 10 of Experiment IV the reverse 

 condition obtained, for we found that in this abnormal oyster 

 the B. typhosus had considerably increased, whereas in the 

 abnormal cockle 14 we found the smallest number of B. 

 typhosus in the whole series. This would suggest that the 

 B. typhosus thrives in the cockle well so long as this animal 

 is in a normal state a suggestion which is borne out in a 

 decided manner by the analysis mentioned in the foregoing 

 Experiment V, for we find that in the cockles after two, five, 

 and particularly after six days' change the number of B. 

 typhosus had gradually risen. After one day's change their 

 number had fallen from 500,000 to 153,000 ; then it rose, till 

 after six days' change it had surpassed by more than three- 

 fold the number of B. typhosus in the first cockle, having 

 risen from 500,000 to 1,540,000. In a former report (I.e.) I 

 had already observed this phenomenon of increase of B. 

 typhosus in the cockle as time went on; here we have 

 definite proof by numerical evidence. 



The cockle, then, differs in a dangerous way from the 

 oyster, inasmuch as not only is the cockle not capable of 

 dealing so well with the ingested B. typhosus as the oyster, 

 but it appears to offer to the B. typhosus even facilities for 



E 



