CHANNELS OF INFECTION 19 



as trichinosis is contracted by eating pork containing 

 living trichinae. As these parasitic worms are promptly 

 killed at a comparatively low temperature, cooked 

 pork is quite harmless, so far as this disease is con- 

 cerned. 



Infection through wounds is far less common at 

 the present day than was the case before aseptic sur- 

 gery and the antiseptic treatment of wounds became 

 established as a standard method of surgical proced- 

 ure. Formerly epidemics of septicaemia, erysipelas, 

 and hospital gangrene were of frequent occurrence, 

 and the cleanest and best regulated hospitals were 

 not exempt from these visitations. But in the light 

 of our present knowledge such epidemics are no 

 longer excusable and the infection of surgical wounds 

 is extremely rare. Accidental wounds may, however, 

 become infected at the time they are inflicted or be- 

 cause of failure to apply proper surgical dressings. 

 Jagged and penetrating wounds which do not bleed 

 are especially liable to be infected by the lodgment 

 of germs in the deeper portion of the wound. It is 

 in this way that tetanus or lockjaw is commonly pro- 

 duced. The tetanus bacillus forms spores which may 

 retain their vitality for years. These are found in 

 soil which has been enriched by manuring and in the 

 dust of streets. 



Bubonic plague is another disease which is com- 



