726 DISTRIBUTION AND HABITAT OF THE BACTERIA. 



Some of the 

 intestinal 

 bacteria do 

 not grow in 

 the ordinary 

 cultures. 



from the contents of some part or other of the 

 intestinal canal, or from the secretions of the mouth, 

 we see a much greater number of varieties of "bacteria 

 than when the bacteria contained in the same specimens 

 are isolated by our ordinary methods of cultivation. 

 It is evident that only a small fraction of the bacteria 

 which are present develop. It is by no means clear 

 what is the cause of this result of cultivation. Some of 

 the bacteria which do not, appear in the ordinary culti- 

 vations are evidently anaerobes, and a markedly better 

 development of bacteria is often obtained when the 

 material is cultivated in the absence of air. Others of the 

 bacteria which are seen and stained in the microscopical 

 preparations have probably been so affected by the action 

 of the gastric juice, or of the organic acids of the intes- 

 tinal contents, that they grow very slowly, and only in 

 specially favourable fluid nutritive media; hence Buclmer 

 was able to cultivate a greater number of varieties from 

 the intestinal contents by the employment of isolated 

 cultivation in fluid media, and by carrying on the culti- 

 vation for a longer time than when he limited himself 

 to jelly plates. It is also possible that the mucous 

 membrane may exert some inhibitory influence on the 

 bacteria, and that this may continue even after their 

 inoculation into cultures. 

 Absence of While the external and internal surfaces of the body 



bacteria in the . , , TI-.TI r* n 



interior of the are thus richly supplied with bacteria we find none in 

 healthy body. tlie j n t e rior of the body under normal conditions (see 

 p. 83). It is only when parasitic organisms have 

 penetrated into the body, and have set up disease there, 

 that we have the presence of specific bacteria either in 

 Exceptions, the blood or in various organs. Further, Wyssoko- 

 witsch has shown that bacteria may be temporarily 

 present in an apparently quite normal body when 

 bacteria, either saprophytes or at any rate species not 

 infective for the animal in question, have penetrated 

 into the blood through a wound. Such bacteria are 

 deposited chiefly in the liver, spleen, and medulla of 

 bone, and remain there in a living condition for a 

 length of time varying from a few hours to days, while 



