J. Henderson Smith 



J9 



successful inoculation being obtained, and that even fully virulent 

 organisms may fail to produce infection when given in a small dose. 



It is perhaps rather surprising that the change in the number of 

 spores present should make so nmch difference in the times required 

 to kill. The average dimensions of the spores used are about 10 /x long 

 by about 8 fi broad. Each spore certainly weighs less than a piece of 

 flint of the same size would weigh. But if we assume that the spore is 

 a sphere lOyu in diameter and that each spore has a weight of the same 



No. 

 survivors 



100 



80 



60 



40 



20 



Minutes 20 



40 



60 



80 



100 



120 



140 



160 



Fig. 4. Phenol 0-4 per cent. 



O O 2,700,000 spores in 1 c.c. X -- X 1,000,000 spores in 1 c.c. 



O O 11,400 spores in 1 c.c. X X 5000 spores in 1 c.c. 



order as flint, viz. three times that of water — and this is greatly to 

 exaggerate the weight of the spores — we have in a 0-4 per cent, phenol 

 mixture, containing 1,000,000 spores in each 1 c.c, two and a half times 

 as much weight of phenol as of spores. In a 0-7 per cent, mixture with 

 the same number of spores there is present four times as much weight 

 of phenol as of spores. We cannot suppose that the individual spore 

 will take up nearly its own weight of phenol. I have not yet succeeded 

 in estimating directly the amount of phenol actually removed from such 

 solutions by the spores, for the quantities concerned are very minute. 



