COMBATING PARASITIC BACTERIA. 173 



curs. At first it was thought that the air was the 

 great source of infection, but the air bacteria have 

 been found to be usually harmless. It has ap- 

 peared that the more common sources are the 

 surgeon's instruments, or his hands, or the cloth- 

 ing or sponges which are allowed to come in con- 

 tact with the wounds. It has also appeared that 

 the bacteria which produce this class of troubles 

 are common species, existing everywhere and uni- 

 versally present around the body, clinging to the 

 clothing or skin, and always on hand to enter the 

 wound if occasion offers. They are always pres- 

 ent, but commonly harmless. They are not for- 

 eign invaders like the more violent pathogenic 

 species, such as those of Asiatic cholera, but may 

 be compared to domestic enemies at hand. It is 

 these ever-present bacteria which the surgeon 

 must guard against. The methods by which he 

 does this need not detain us here. They consist 

 essentially in bacteriological cleanliness. The 

 operation is performed with sterilized instruments 

 under most exacting conditions of cleanliness. 



The result has been a complete revolution in 

 surgery. As the methods have become better 

 understood and more thoroughly adopted, the in- 

 stances of secondary troubles following surgical 

 wounds have become less and less frequent until 

 they have practically disappeared in all simple 

 cases. To-day the surgeon recognises that when 

 inflammatory troubles of this sort follow simple 

 surgical wounds it is a testimony to his careless- 

 ness. The skilful surgeon has learned that with 

 the precautions which he is able to take to-day 

 he has to fear only the direct effect of the shock 

 of the wound and its subsequent direct influence; 

 but secondary surgical fevers, blood poisoning, 

 12 



