278 SUMMARY OF CURRENT RESEARCHES RELATING TO 



carbon and nitrogen the lower fungi most readily derive those elements. 

 The general results may be stated as follows : — 



As resjiects nitrogen, all those compounds may be regarded as 

 favourable which are comprised under the general terms amides and 

 amines, whether the oxygen is also consumed or not. While aceta- 

 mide, methylamine, ethylamine, propylamine, asparagin, and leucin 

 supply both carbon and nitrogen, the latter only is absorbed from 

 oxamide and urea. All ammoniacal salts are also available to fungi 

 as sources of nitrogen, while some also make use of nitrates. Free 

 nitrogen is useless, nor can it be absorbed out of cyanogen or of any 

 compounds in which it is present only in the form of cyanogen. 

 When this is apparently the case, it results from ammonia having 

 been first formed. 



As a general statement respecting the nutritive power of nitrogen- 

 compounds, it may be said that nitrogen is most easily assimilated 

 when present as NH2, loss so when in the form of NH, and still less 

 so as NO, while it cannot be assimilated at all if combined with any 

 other element than H or 0. From such compounds the oxidizing 

 action of fungi may, however, produce a substance of the group NO, 

 which is subsequently reduced to one of the NH^ series. 



Carbon can be absorbed from a great variety of organic com- 

 pounds ; with access of oxygen almost all carbon compounds are 

 nutritive, whether acid, alkaline, or neutral, provided they are soluble 

 in water and not too poisonous. Amongst the few that are not useful 

 in this way are CO2, cyanogen, urea, formic acid, oxalic acid, and 

 oxamide. The assimilable carbon-compounds contain the element 

 in the form of CHj or CH ; and it is probable that the latter group 

 are available only when two or more atoms of C with which H is 

 combined are also directly in combination with one another. For 

 example, methylamine (with 1 C and 3 H) and benzoic acid (with a 

 chain of C atoms, each with 1 H) are nutritive, while formic acid 

 (with only 1 C and 1 H), and methyl-alcohol, are not. Carbon 

 cannot be assimilated when directly in combination, not with H, but 

 with some other element, as in the cyanogen group, urea, oxalic acid, 

 and oxamide, where only atoms of N, 0, and C are in direct combina- 

 tion with the C. 



Irrespectively of the chemical constitution of the nutrient substance, 

 the living cell will, imder similar circumstances, most readily absorb 

 those substances which are the most readily detached from their 

 compounds, and therefore require the least force. Prof. Naegeli has 

 drawn up the following list of the most frequent sources of nitrogen 

 and carbon, advancing from those which are most favourable to those 

 that are least so : — 1, Albumen (peptone) and sugar ; 2, leucin and 

 sugar ; 3, ammonium tartrate or sal-ammoniac and sugar ; 4, albumen 

 (peptone) ; 5, leucin ; 6, ammonium tartrate, ammonium succinate, 

 asparagin ; 7, ammonium acetate. 



Pathogenous Fungi in the Animal Organism.* — In previous 

 publications Dr. P. Grawitz has shown the remarkable similarity, in 



* Arch. Path. Anat. Physiol. (Virchow), Ixxxii. (1880) pp. 355-76. 



