WHY WE DIE. 



87 



ordinarily rapidly by mere division. There are two chief cccci 

 which are pathogenic in man : — 



(a) The taphylococcus, so called because when these cocci 

 divide, the colony formed holds together like a bunch 

 of grapes. 



(6) The streptococcus, so called because when these cocci 

 divide, the colony formed holds together like a string. 



The bacillus is a minute rod-shaped bacterium. It multiplies 

 either by fission, or by spores. There are many varieties of 

 bacilli which are pathogenic in man, for example : — 



(a) The tubercle bacillus, producing numerous lesions, 



including phthisis. 

 (6) The enteric bacillus, producing enteric or typhoid fever, 

 (c) The tetanus bacillus, producing tetanus or " lock-jaw." 



The spirillum is really a curved bacillus, and is but rarely 

 pathogenic in man. 



All types of bacteria tend to kill their host by the production 

 of toxins. These are specific poisons produced by the bacteria 

 during their life and reproduction in the living tissues. These 

 toxins are either intracellular, remaining closely associated with 

 the bacterium and acting locally, as is the case with the tubercle 

 bacillus, or extracellular, passing into the blood or lymph stream, 

 and acting distantly from the bacterium as is the case with the 

 tetanus bacillus. 



There are two ways in which the human tissues are able in 

 many cases to withstand the onslaught of bacteria. 



The tissues, especially the white cells of the blood, actually 

 kill the bacteria ; it is, in fact, a pitched battle between cell and 

 parasite. Or there is produced in the blood an anti-toxin which 

 neutralises the toxin, just as in chemistry an alkali neutralises 

 an acid. An antitoxin can be artificially prepared outside the 

 body ; and on being injected it often serves its purpose, and 

 renders the toxin harmless. 



The War against Bacteria. 



It is wonderful, seeing the multitude of bacteria that surround 

 the human being, that the tissues are able to withstand them. 

 It is only when the phagocytes — the special white cells of the 

 blood — are fit, and therefore able to do their duty efl&ciently, 

 that the blood is able to overcome the bacterial invasion. Any 

 condition which makes these cells feeble, is a menace to the human 



