682 



CONSTANCY AND MUTABILITY OF FUNGI. 



The loss of 

 the power of 

 bacteria to 

 excite disease 

 and fermenta- 

 tion. 



It would be 

 necessary to 

 regard attenu- 

 ation as a 

 degenerative 

 process if it 

 were not 

 hereditary. 



laws which have heen made out with regard to the higher 

 organisms. The power possessed by many "bacteria of 

 multiplying in the body of living warm-blooded animals, 

 as well as the property of others of exciting fermenta- 

 tion in suitable substrata, have, as has been above men- 

 tioned (p. 656), proved extremely labile in many species 

 of bacteria, and can be destroyed by numerous in- 

 fluences, such as high temperatures, chemical poisons, 

 &c., which cause degeneration of the organisms. In- 

 deed, the repeated passage of certain parasitic bacteria 

 through more or less suitable hosts appears, according 

 to Pasteur's experiments, to lead to increase or diminu- 

 tion in their virulence,* and in the case of glanders, for 

 example, a cultivation for a certain length of time on 

 potatoes, which is otherwise the most suitable dead 

 nutrient material for their growth, suffices to lead to 

 complete disappearance of their virulence (Loeffler). 



This "attenuation" of the lower fungi would not be of 

 much importance if we had only to do with a degenera- 

 tive process which had arisen under the influence of the 

 abnormal conditions of life employed, and which was 

 only retained so long as these conditions acted, and 

 was not hereditary through a long series of genera- 

 tions under normal conditions, but was rapidly lost. 



* A similar alteration of pathogenic properties of the lower organisms 

 TOas formerly stated to occur by Davaine as the result of his experi- 

 ments on progressive virulence. Davaine thought that he had observed 

 that the virulence of septicaemia bacilli constantly increases the oftener 

 they are inoculated from one animal to another; thus, while of an 

 infective fluid found accidentally several drops are necessary to insure 

 infection in the first instance, yet, when it has been inoculated from 

 animal to animal for a considerable time it is ultimately found that the 

 minutest fraction of a drop is sufficient to cause the fatal disease. 

 Koch and Gaffky (Mittheil. a. d. Kais. Ges. Ami., vol i.) were able to 

 demonstrate that in the case of several bacteria which occasioned 

 septicaemia no such progressive increase in virulence existed ; that it 

 was only necessary to employ larger doses at first, when the material 

 used for inoculation was very impure and only contained a few of the 

 pathogenic organisms ; that, on the other hand, when the material was 

 pure the same dilution was as active at the commencement of the series 

 of experiments as at the end. More recent experiments of Pasteur as 

 regards swine erysipelas, hydrophobia, &c., point, however, to the fact 

 that some species of bacteria undergo marked alterations in virulence 

 as the result of their passage through the bodies of certain warm- 

 blooded animals. 



