664 FUNGI 



(Plate XIV). The inoculated bacteria, instead of moving freely, as 

 they would in a liquid medium, are fixed to one spot, where they 

 develop ' colonies ' in a characteristic manner, showing their own 

 morphological features (fig. 502). Cleanliness and care, as well as 

 practice in manipulation, are essential. In the same way we can only 

 allude to the investigation of the chemical products of bacteria, such 

 as toxins, and to those antidotal substances or antitoxins which 

 develop in the blood of suitable animals inoculated with gradually 

 increasing doses of toxins. Antitoxins and vaccines are now largely 

 used in the treatment of tetanus, diphtheria, typhoid fever, plague, 

 cholera, and septic diseases in the human subject. 



The pathological and therapeutic value of these researches is 

 far beyond our present ability to estimate, and must have an 

 apparently increasing value. But it is a science with which a work 

 of this sort may not deal further than to show the light use of the 

 microscope and its appliances, by which the work of pathological 

 bacteriology can alone be successfully done. 



