MORPHOLOGY AND BIOLOGY OF BACTERIA. 25 



Of late, attention has been directed to ramification, club- 

 formation, and granular disintegration occurring among 

 tubercle-bacilli and diphtheria-bacilli, and strongly sugges- 

 tive of streptothriceae. Upon the basis of such observations 

 a number of authorities have concluded that the exciting 

 agents of diphtheria and of tuberculosis, together with the 

 whole actinomyces-group, belong to the hyphomycetae. 

 Such classification must, however, be considered as prema- 

 ture ; although the presumption is justified that the tubercle- 

 bacillus and the diphtheria-bacillus stand in kindred rela- 

 tionship to the ray-fungus and the group of organisms 

 represented by it. 



Involution-changes must not be confounded with variabil- 

 ity in form of growth. The former take place when the 

 nutritive medium is exhausted and the bacteria begin to die ; 

 the cells then swell, become thick and plump, show defi- 

 ciencies, and undergo disintegration and other changes of 

 allied nature. Whether all of the resulting peculiar forms 

 are to be attributed to degenerative changes is a question 

 that must, at least, be left open for the present. It is quite 

 possible that the very large, so-called giant-cells result 

 rather in consequence of especially favorable vital conditions. 

 Other involution-manifestations appear to be due to special 

 functions of the bacteria, such as their fermentative activity. 

 In this manner are perhaps to be explained the involution- 

 forms of the acetic bacterium, and especially of numerous 

 microbes that are cultivated in media containing grape-sugar. 



Bacteria are ubiquitous : they are found everywhere ; 

 only the internal organs of the human and the animal body 

 not in communication with the atmosphere are free from 

 them. Some of the pathogenic germs confine their activi- 

 ties to certain living organisms, so that their area of dis- 

 tribution is, in consequence, a restricted one. 



For their sustenance the bacteria require preformed or- 

 ganic carbon-compounds, as most of them, by reason of 

 their deficiency in chlorophyl, are capable of utilizing the 

 carbon dioxid of the atmosphere. They require also nitro- 

 gen-compounds, which they can obtain from organic sub- 

 stances, as well as from inorganic nitrates and ammonia- 

 compounds. It need scarcely be added that water is neces- 

 sary for the development of the bacteria. The nutritive 

 material for the bacteria must be feebly alkaline or neutral, 

 as in general they do not develop so well upon acid media. 



