50 MINERAL NUTRIENT MATERIALS. 



is furnished by various substances devoid of phosphorus — 

 many all)uminoids in particular — so that it is impossible to 

 obtain by this method any reliable differentiation, especially 

 between the nuclein-like and the albuminoid constituents of 

 the cell. 



The question how far phosphorus can be replaced as a food- 

 stuff by its ally, arsenic, after having been answered in the 

 negative by J. Stoklasa for the higher phanerogams, and by 

 H. MoLiscH (IV.) for different algae, was examined by E. 

 GuENTHER (I.) in connection with Bhizopus ni<jricans, the same 

 result being obtained. This notwithstanding, compounds of 

 arsenic are attacked and assimilated by many fungi, provided 

 they are present in insufficient quantity to exert any poisonous 

 action. B. Gosio (II.) was the first to show that Penicillium 

 glaticum, AfijjeiyiUus r/laucus, Asp. virens, Miicor viucedo, M. 

 racemosus, Cephalofliecium roseum, and others, in suitable nutrient 

 media will convert arsenious acid into volatile compounds 

 having an odour of garlic, and with such a degree of cei'tainty 

 that an addition of 0.02 m.g. of Na.jAsOg can be detected in 10 

 c.c. of milk by this means. This new fact is of practical interest 

 to official chemists and hygienists, in connection with the toxic 

 phenomena produced by wall papers, &c., containing arsenic. 

 The chief literature on this subject has been collected by R. 

 Abel and P. Ruttexberg (I.). Attempts have been made to 

 explain these phenomena by assuming that the printed arsenical 

 pigments come oft' in the form of dust ; and this view was 

 recently accepted by 0. Emmerlixg (I.), since neither he, nor 

 G. ISIarpmann (V.) since, have succeeded in liberating arseni- 

 nretted hydrogen from cultures of the aforesaid fungi (or of 

 Mucor corymhifer and Aspergillus fumigatus), on arseniferous 

 nutrient media. On the other hand, the probability that 

 volatile organic compounds of arsenic are formed has been 

 shown by Gosio (IV.) ; and one such has been made known by 

 P. BiGiXELLi (I.) as dimethylarsine, As(C2H5)^IT, which is a 

 near ally of the extremely poisonous substance cacodyl and 

 emits an odour of gai'lic. The advantage accruing to the analyst 

 from Gosio's observation is the possibility of replacing the 

 Mai'sh test for arsenic by a shorter, microbiological method, 

 wherein the substance under examination can be tested without 

 the necessity for a tedious preparation (destructive of the 

 organic matter !). The method as recommended by Gosio is 

 performed in the following manner : A cut is made in a clean 

 piece of raw potato, and after inserting therein a little of the 

 substance (e.g. aniline dyestuff) to be tested for arsenic, the 

 potato is placed in a Roux test glass (potato glass) and sterilised 

 for fifteen minutes under a pressure of one atmosphere. Abel 

 and Buttexberg (I.) recommend the employment of a pap made 

 from the cmmb of white or brown bi'ead and contained in an 



