300 EFFECT OF CHEMICAL AGENTS [Cn. XI 



organisms. The cultures were then reared either in complete darkness or 

 in dim light. The precautions taken to eliminate organic matters would 

 seem to be complete ; but those who know the difficulties of such experi- 

 ments seem willing to admit the possibility " that exceedingly minute quan- 

 tities of organic nitrogen and carbon are actually present " (JORDAN and 

 RICHARDS, '91, p. 880). On the other hand, "exceedingly minute quanti- 

 ties " of organic matter could hardly account for the vigorous growth of bac- 

 teria ; and, in general, a priori objections cannot be permitted to overthrow 

 results gained by the use of methods which are beyond reproach. 



The organisms placed in this water, deprived of the last 

 traces of organic matter, developed rapidly, but not quite so 

 rapidly as organisms placed in natural water to which the 

 necessary salts had been added. Analysis showed that not only 

 nitrates but also organic carbon compounds had been formed. 

 Thus the careful experiments of WINOGRADSKY demonstrate 

 what the less critical experiments of HER^EUS ('86) had 

 already rendered probable, that a complete synthesis of organic 

 matter may take place through the action of living beings and 

 independently of the solar rays. These noteworthy observa- 

 tions, then, obliterate the last sharp line of distinction between 

 the nutritive processes of chlorophyllaceous and non-chloro- 

 phyllaceous organisms. We may now state that the elements 

 C, H, N, and O may be gained from complex organic food 

 materials by all organisms, and from simple compounds, such 

 as carbonic acids, ammonia, and water, by all chlorophyllaceous 

 organisms, and, very probably, by certain non-chlorophylla- 

 ceous ones also. 



The elements other than 0, H, N, and O are probably 

 gained by chlorophyllaceous and non-chlorophyllaceous organ- 

 isms alike, from either inorganic or organic compounds con- 

 caining the necessary elements ; although, possibly, animals 

 make use of the metals more readily when they are in organic 

 compounds. Suitable proportions of the different metals in a 

 nutritive solution for green plants are given in the following 

 tables, showing various standard solutions employed by differ- 

 ent experimenters : 



