270 BACTERIA 



a word must be said of that remarkable application of pre- 

 ventive medicine known as the antiseptic treatment of 

 wounds. When Lord Lister was Professor of Surgery in 

 Glasgow, he was impressed with the greatness of the evil of 

 putrefaction in wounds, which was caused, not by the 

 oxygen of the air, as Liebig had declared, but by the en- 

 trance into the wound of fermentative organisms from the 

 air. This was demonstrated by Pasteur, who pointed out 

 that they could not arise de novo in the wound. Hence it 

 appeared to Lister that these fermentative bacteria which 

 produce putrefaction in wounds must either be kept out of 

 the wound altogether, or killed, or their action prevented, 

 in the wound. To keep air away from wounds is an almost 

 impossible task, and thus it came about that wounds were 

 dressed with a solution of carbolic acid. 



From time to time examples occur of bacterial disease 

 being directly inoculated in wounds made with polluted in- 

 struments, or in cuts made by contaminated broken glass, 

 or in gunshot wounds. Tetanus is, of course, one of the 

 most marked examples. 



3. Contagion is a term which has suffered from the many 

 ways in which it has been used. Defined shortly and most 

 simply, we should say a disease is contagious when it can be 

 *' caught" by contact, through the unbroken surfaces, be- 

 tween diseased and healthy persons. Ringworm is an 

 example, and there are many others. 



4. The Alimentary Canal: Food, The recent Royal 

 Commission on Tuberculosis has collected a large mass of 

 evidence in support of the view that tubercle may be spread 

 by articles of food. Milk and meat from tuberculous animals 

 naturally come in for the largest amount of condemnation. 

 To these matters we refer elsewhere. 



5. The Respiratory Tract : Air, The air may become in- 

 fected with germs of disease from dusty trades, dried 

 sputum, etc. If such infected air be inhaled, pathogenic 



