THE STORY OF THE BACTERIA. IOI 



whooping-cough, and small-pox which indicates 

 that they too are bacterial diseases ; but the 

 specific organisms causing them have not yet 

 been identified. So that in attempting to 

 guard against their spread we are at present 

 obliged to make what use we can of the facts 

 which we know about the proven bacterial 

 diseases and the experience which has been 

 accumulated by physicians who so long and 

 faithfully have studied them at the bedside. 

 Against small-pox, however, we have a most 

 efficient safeguard in vaccination, although we 

 do not yet know the reason for the marvellous 

 protective effects of the procedure. 



Yellow-Fever. 



Yellow-fever is a disease of the utmost im- 

 portance in some parts of our country, about 

 the cause of which we are almost entirely in 

 the dark. Our knowledge of it is largely con- 

 fined to the characters of the disease as it is 

 seen at the bedside, and to the general con- 

 ditions under which it is liable to occur and 

 spread. In many respects it resembles the 

 known bacterial diseases, in others it differs 



