COLOURING-MATTERS, POISONS, OXIDATIONS. 373 



The injuries set up by species that are pathogenic in plants 

 and animals (Asp. fumigalus, A.jlavus, A. nidulans, Penicilliu'ni 

 luleum, P. glaucum, P. italicum, P. olivaceum) are probably 

 attributable to the production of definite poisons ; but, in the 

 case of those belonging to the second category a list of which 

 was compiled by GUEGUEN (III.) no further particulars are yet 

 available. J. BEHRENS (IX.) also failed to ascertain anything 

 definite with regard to the active substance in the fungi which 

 cause the rotting of fruit, but it is apparently not an enzyme 

 and is non-volatile. A similar role is ascribed to free oxalic acid 

 in the case of Asp. niger, which is said by BEHRENS (XVI.) to be 

 dangerous to plant embryos. LODE (II.) failed to detect any 

 poisonous substance in cultures of species that are pathogenic 

 towards animals. 



In several instances investigations have been made into the 

 destructive action, exerted more particularly by vegetative 

 growths, on readily oxidisable substances, such as organic acids 

 and alcohols. This is related to the previously mentioned fact that 

 oxalic acid, citric acid and ethyl alcohol are decomposed again by 

 the fungi that have produced them (Asp. niger, Penicilliu'ni ^ 

 Citromyces, Allescheria) ; but whether oxydases are concerned is 

 still unknown. So far as the substances in question form suit- 

 able food -stuffs (tartaric acid, citric acid, lactic acid, &c.), this is 

 nothing remarkable ; but it is also exhibited, though to a small 

 extent, in the case of the majority of such substances (acetic 

 acid, butyric acid, propionic acid, &c.) when the degree of con- 

 centration is low. LABORDE (VI.) reports that growths of Alles- 

 cheria (Eurotiopsis) slowly decompose oxalic acid, malic acid (even 

 when 2 per cent, is present), acetic acid (2 per cent.), propionic 

 acid, butyric acid (0.8 per cent.), valeric acid (0.6 per cent.) and 

 formic acid (to i percent.), whereas inactive lactic acid was rapidly 

 decomposed (even with 5 per cent.) without being split up into 

 its active components (see vol. i. p. 232), and also methyl, propyl, 

 butyl and amyl alcohol in small quantities. According to 

 DUCLAUX (I.), growths of Asp. niger will decompose even 8-10 

 per cent. (?) of acetic acid, and also lactic acid and butyric acid 

 (0.1-0.2 per cent., of which 0.5 per cent, is the smallest fatal 

 dose. In presence of butyric acid or tartaric acid, the acetic acid 

 was consumed more rapidly than either. Whether, as stated by 

 Duclaux, Asp. niger in cultures free from bacterial infection is 

 really capable of converting calcium butyrate into carbonate, and 

 calcium lactate into carbonate and oxalate, is a point that needs 

 closer examination, the mere statement being scarcely sufficient. 

 Formic acid, in quantities up to 0.08-0.09 per cent , is decomposed 

 by Asp. niger and Penic. glaiwum, though according to Duclaux 

 larger doses (0.12 per cent.) have an injurious effect, whilst, 

 according to Wehmer, up to 10 per cent, of citric acid, tar- 

 taric acid and malic acid are decomposed by both fungi. In this 



