SANGER. — VOLATILE COMPOUNDS OF ARSENIC. 145 



The reagents used in Exps. 17 b and 18, being in another labora- 

 tory, were subjected to the same rigid tests, and the absence of arsenic 

 was proved. The dishes and utensils were proved free by blank 



tests. 



Discussion. 



The scope of this paper has gone far beyond my original intention, 

 which, as st.ated above, was simply to repeat the work of Fleck and of 

 Hamberg. As the important results of Hamberg and of Gosio have 

 not been given the publicity due to them, not to speak of the compara- 

 tive obscurity into which the work of many of the other investigators 

 has fallen, I feel that the somewhat protracted review of the work 

 that I have here presented will make the subject clearer, and will 

 serve to place more surely beyond cavil the fact that a gaseous or 

 volatile compound of arsenic may be generated from decaying ar- 

 senical matter ; hence the possibility of chronic poisoning from the 

 presence of such a compound in the air of rooms papered with arseni- 

 cal paper. 



Of the experiments mentioned in the historical sketch, those of 

 Schmidt and Bretschneider, Fleck, Hamberg, Selmi, Bischoff, Gigli- 

 oli, and Kinnicutt are the most important. The others need not be 

 considered, either because there was little or no chance in them for 

 decomposition by mould, or on account of imperfect methods of ex- 

 perimentation or analysis. In the cases of Hamberg and Bischoff 

 there was undoubtedly a volatile compound formed, though Hamberg 

 proved it and Bischoff did not. Fleck and Selmi do not show con- 

 clusively that it was present. 



The adverse results of the other four investigators, as well as those 

 of my first series, are very easily explained. There was either too 

 much arsenic for the arsenio-bacteria to tolerate, or else the latter 

 were not present. It is worthy of note that, with the exception of 

 Hamberg's experiments, whenever the unsterilized matter was allowed 

 to decompose in a closed vessel, no arsenical compound was evolved, 

 while exposure to spontaneous inoculation in the air developed an odor. 

 This would seem to point to a tolerance when fresh germs can gain 

 access to the material. In my own case I am inclined to think that 

 absence of the specific bacteria was the chief reason for failure, though 

 in many cases I used large amounts of arsenic. As to my experiments 

 on the air of rooms, it is quite possible to explain the negative results 

 by the choice of reagents and the amount of air aspirated. We have, 

 however, sufficient evidence from Hamberg on this point. 

 vol. xxix. (n. s. xxi.) 10 



