DISEASE BACTERIA 155 



may get into the blood stream through the wound 

 and thus be carried through the body, bringing about 

 septiccBmia (blood poisoning). 



The immense progress of modern surgery has been 

 made possible, first by the use of antiseptics, i.e. by treat- 

 ing the wound with a substance (such as weak carbolic 

 acid) which destroys the bacteria. The introduction 

 of the use of these in surgery was due to Joseph Lister 

 (afterwards Lord Lister), and resulted in a great decrease 

 in the death-rate of surgical patients from blood poison- 

 ing. Later on aseptic methods of surgery were intro- 

 duced, in which the surgeon's hands, instruments and 

 dressings used are carefully sterilised, and the wound 

 thus kept free from all bacteria. 



Besides the Streptococci and Staphylococci, other 

 kinds of bacteria may be introduced into wounds con- 

 taminated with soil rich in dung, and cause such specific 

 diseases as tetanus {Bacillus 'tetani) and gas-gangrene 

 {Bacillus welchii), so called because of the large amount 

 of gas produced in the wound by the action of the 

 bacillus on the tissues. These are both spore-producing 

 bacilli which inhabit the intestines of horses and cows, 

 where they do no harm. The spores persist for a long 

 time in the manured soil, and germinate when they 

 enter the wound, producing active cells which form 

 dangerous toxins that often lead to death. 



In the case of most " infectious " diseases, human 

 beings directly or indirectly infect one another with 

 spores or active cells of various pathogenic species, 

 and these give rise in the body to different specific 

 toxins which cause the symptoms of the corresponding 

 disease. Some of the most serious among them are 

 tuberculosis in its various forms {Bacillus tuberculosis), 

 syphihs {Spirochete pallida), typhoid or enteric fever 



