2/2 BACTERIA 



period the signs of the disease assert themselves. Professor 

 Watson Cheyne and others have maintained that there is 

 some exact proportion between the number of bacteria 

 gaining entrance and the length of the incubation period. 



Speaking generally, we may note that pathogenic bacteria 

 divide themselves into two groups: those which, on enter- 

 ing the body, pass at once, by the lymph or blood stream, 

 to all parts of the body, and become more and more diffused 

 throughout the blood and tissues, although in some cases 

 they settle down in some spot remote from the point of en- 

 trance, and produce their chief lesions there. Tubercle and 

 anthrax would be types of this group. On the other hand, 

 there is a second group, which remain almost absolutely 

 local, producing only little reaction around them, never 

 passing through the body generally, and yet influencing the 

 whole body eventually by means of their ferments or toxins. 

 Of such the best representatives are tetanus and diphtheria. 

 The local site of the bacteria is, in this case, the local man- 

 ufactory of the disease. 



Whilst the mere bodily presence of bacteria may have 

 mechanical influence injurious to the tissues (as in the small 

 peripheral capillaries in anthrax), or may in some way act 

 as a foreign body and be a focus of inflammation (as in 

 tubercle), the real disease-producing action of pathogenic 

 bacteria depends upon the chemical poisons (toxins) formed 

 directly or indirectly by them. Though within recent years 

 a great deal of knowledge has been acquired about the 

 formation of these bodies, their exact nature is not known. 

 They are allied to albuminous bodies and proteoses, and are 

 frequently described as tox-albumens. It may be found, 

 after all, that they are not of a proteid nature. Sidney 

 Martin has pointed out that there is much that is analogous 

 between the production of toxins and the production of the 

 bodies of digestion. Just as ferments are necessary in the 

 intestine to bring about a change in the food by which 



