OF THE HUMAN SUBJECT. 23 



ments, there grow out one or more processes or buds, which, 

 after increasing to a certain size, may become abstricted off and 

 disconnected from the parent cell, or whilst acquiring an inde- 

 pendent cavity, may remain connected with it and generate 

 further elements by the same plan. The hyphomycetes occupy 

 a higher position than either of the foregoing groups, in that 

 they present distinct organs of fructification, and are capable, 

 moreover, of a proper sexual process of propagation. 



Not that these subdivisions are more clearly defined than 

 are others in biology. 



The branching filamentous forms, at times met with in the 

 tubercle and tetanus bacillus, make an approach toward the 

 mycelial productions of moulds; and in actinomyces and strep- 

 tothrix Madurae, a dense and branched mycelium is regularly 

 developed in artificial cultures. 



The microscopic characters of bacteria are in scarcely any 

 case sufficient to allow of their identification. It is by the en- 

 semble of their cultural characters on different media, their chem- 

 ical products, the results of experimental inoculation upon ani- 

 mals, that identification is possible, and to these must be added 

 the effects produced upon bacteria by the action of specifically 

 immunized sera. 



Accumulated observations have disclosed a bacterial king- 

 dom of such dimensions that to determine or identify any given 

 individual is a matter of increasing difficulty. The problem of 

 identification is reduced, however, within comparatively easy 

 limits when those organisms which are pathogenic are alone con- 

 sidered, and still more so when attention is restricted to those 

 that cause disease in the human subject. 



The fundamental argument adopted by Darwin for the 



