562 



VITAL ACTIONS OF THE LOWER FUNGI. 



Dependence 

 of the forma- 

 tion of the 



although otherwise the growth of the fungi is not 

 affected. Hence the probability is that these pigments 

 are not produced as such by the fungi, but that the latter 

 colouring f orm a chromogenic substance which becomes converted 



matters on the 



entrance of into the colouring matter only as the result of the action 

 Influence of of x jgen. Not uncommonly we notice different shades 

 th t 1 i ut ? ent of the pigment, and at times even marked differences in 



substratum . 



on the forma- the colour when the organisms are grown on different 

 nutrient substrata ; this is evidently due to the influence 



pigment. 



Chemical 

 nature of the 

 pigments. 



Products of 

 fermentation 



of the different substrata, and of their reaction on the 

 chromogenic substance. Such variations in the pigment 

 are well seen in connection with the bacilli of blue milk. 

 Very often a difference in the colour of a cultivation is 

 due to contamination with other fungi ; and this point 

 must always be carefully tested before we refer the 

 difference to the influence of the nutrient substratum. 



But little has been ascertained as to the precise nature 

 of these pigments ; with regard to most of them we only 

 know a few reactions which have already been referred 

 to in the systematic part of this work. The colouring 

 matter, which has been most completely investigated, is 

 that of greenish blue pus, pyocyanine ; Gessard ascer- 

 tained that chemically this substance was a base which 

 was closely related to the ptomaines ; the sulphate 

 and chloride salts crystallise in the form of reddish 

 needles, a crystalline precipitate is also deposited 

 from their solutions by chloride of gold, chloride 

 of platinum, iodide of potash, and mercury, further 

 by tannin, chloride of mercury, and phosphoric molybdic 

 acid. From a mixture of ferro-cyanide of potash 

 and chloride of iron pyocyanine gradually throws down 

 a precipitate of Berlin blue, but more slowly than 

 morphine. 



We have further to consider the specific products of 

 fermentation which are limited to certain bacteria. 

 Many of these, such as lactic acid, butyric acid, nsthylic 

 alcohol, &c., occur, it is true, very frequently as products 

 of tissue change and of fermentation, but nevertheless, 

 when we take into account the quantity of these products 

 and their relation to each other, we must look on them 



