142 BACTERIA IN RELATION TO DISEASE 



keep the intestine germ-free for a considerable time, and the animals 

 remain notwithstanding in perfect health. This would certainly not be 

 the case if a symbiotic relationship subsisted between the bacteria and the 

 organism. Such a view is contradicted also by the nature of the products 

 arising from bacterial action. They are quite unfitted for resorption and 

 utilization by the animal body. 



The intestine of the new-born infant is absolutely sterile (122), but 

 bacteria make their appearance in a very few hours after birth, even before 

 any nourishment is taken. No less than seven different species have been 

 isolated from the intestine of children before feeding. The first to appear 

 is the B. coli commune, which takes up its post at once in every mortal 

 on his entrance into the world, and remains his faithful companion until 

 death. Whence this ever-present species comes is not known, but it is 

 in all probability a metatrophic aquatic form. If infants be fed with the 

 bottle the lactic acid bacteria appear at once in the faeces, and with every 

 new kind of food new species of bacteria are added to the flora of the 

 alimentary tract. As long as the mucous membrane is uninjured these 

 bacteria are quite without danger for the body (123). Once let the continuity 

 of the epithelium be destroyed however, even at a single point, and grave 

 pathological changes may be set up, for among the hosts of metatrophic 

 bacteria inhabiting the intestine some (e. g. B. coli] are facultative parasites 

 and originators of disease. 



It has long been customary to designate as 'infectious diseases' (124) 

 all those in which the entrance of a certain 'something' into the body was 

 a necessary condition for the existence of the complaint, this 'something,' 

 the pathological 'virus,' playing a part in disease similar to that of the 

 ' ferment ' in the fermentation proce.-ses. Before we knew anything of 

 bacteria it was usual to speak of a contagium when the disease could be 

 transferred only by contact with a diseased individual, and of a miasma 

 when the supposed virus could be carried by the air. And just as the 

 discovery of the ferment organisms displaced the old conceptions of a 

 lifeless ferment, so did the discovery, about the middle of the century, 

 of a ' contagium vivum ' take the place of the old ideas respecting the 

 origin of infectious and epidemic disease. We now know that in the 

 majority of infections the virus animatitin is a bacterium. 



The demonstration of bacteria in the blood or body fluids of a diseased 

 animal is an easy matter where large species are concerned, such as the 

 anthrax parasite. These can be seen even in the fresh blood as pale rods 

 lying about between the blood-corpuscles ; in this way they were discovered 

 in 1850. More minute forms, particularly cocci, which are easily confounded 

 with albuminous granules from the blood, must be rendered visible by 

 staining with aniline or other dyes. Diseased tissues must be fixed, 

 hardened, cut in sections, and stained in order to render the bacteria in them 



