46 THE BACTERIAL CELL. 



37. Quantitative and Qualitative Selective Power. 



The proportions of the constituents present in the available 

 nutriment or nutrient medium supplied seldom correspond to the 

 requirements of the organism which has to make good therefrom 

 losses of substance or energy. It will then take from the supply 

 the substances of which it has need, and leave the residuum entirely 

 untouched, only when the former are present in abundance. This 

 faculty, entitled quantitative selective capacity, is possessed by 

 all living organisms, and among them bacteria. Kappes, in his 

 treatise already referred to, gives very instructive examples of this 

 as well. He compared the composition of the bacterial crop with 

 that of the soil (nutrient medium) in which it was grown ; in this 

 case peptonised meat extract agar-agar. This contained, apart 

 from the 1.5 per cent, of agar-agar, which does not come under 

 further consideration here, altogether 2.5 per cent, of actual 

 nutrient materials, and yielded 0.3 per cent of dry bacterial sub- 

 stance ; that is to say, only 1 2 per cent, of the total nutriment was 

 extracted. The relative proportions of the individual constituents 

 in the medium on the one hand and in the crop on the other 

 proved very different. Thus, for instance, the ratio of CaO : MgO 

 was in the medium 0.70 : 0.44; in the crop, 0.56 : 1.05. Of 

 nitrogenous substances (N x 6.25) the former contained 42.5 per 

 cent, calculated on the dry substance, and the latter 71.2 per cent., 

 and so on. 



The requirements of bacteria in respect of ash constituents 

 were first investigated by KAGELI (IV.), in 1879. SPRENGEL (I.) was 

 admittedly the first to demonstrate that higher plants (Phanero- 

 gamia) absolutely require for the construction of their cells a 

 number of mineral substances, viz., K 2 0, CaO, MgO, Fe 2 O 3 , P 2 5 , 

 S0 3 , all of which must be present, and in sufficient quantity, before 

 the phanerogamic plant can thrive. With the Cryptogamia the 

 case is, however, different. According to Nageli, the fission fungi 

 (tested by him in this connection) are less exacting, since potassium 

 can be replaced by rubidium or caesium without detriment, so far 

 as the fungi are concerned, though not by the alkaline earths. 



Of the latter it is sufficient when one of the following, CaO, 

 BaO, SrO, MgO, is present ; iron can be dispensed with. It follows 

 therefrom that not only quantitative but also qualitative powers 

 of selection are possessed by bacteria. An authoritative confirma- 

 tion of Nageli's discovery is highly desirable, and would prove a 

 very thankworthy task if conjoined with observations on the 

 formative influence of the individual ash constituents. A typical 

 example of this kind of study, alike instructive, stimulating, and 

 worthy of imitation, has been made by Winogradsky on a film 

 yeast, and will be referred to in the second volume. A preliminary 

 step in this direction was taken by A. K. FEDOROLF (I.) in 1895, 

 who, in continuing an investigation commenced by Gamaleja, 



