134 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The result of these fourteen experiments was entirely negative, 

 though they were carried on under widely varying conditions, and by 

 a method better adapted to detect small quantities of arsenic than any 

 before used. On referring to the previous work cited above, the evi- 

 dence seemed to be greatly in favor of the conclusion reached by my 

 own results, the work of Hamberg being the only positive evidence 

 in favor of the formation of a volatile arsenical compound. Yet there 

 were two points that still gave hope of the correctness of the volatile 

 compound theory : first, the clinical evidence of undoubted poisoning 

 where there was no chance for absorption of dust ; and secondly, the 

 fact that in none of the experiments had any quantity of air been 

 tested which approached the amount daily inhaled by an average 

 man.* The amounts used would have perhaps sufficed if the volatile 

 compound were arseniuretted hydrogen, but, supposing it to have been 

 a compound not completely absorbed by argentic nitrate, (as it turns 

 out to be,) a very small amount might have escaped absorption, which 

 as arseniuretted hydrogen would have been easily found. 



Though I did not consider the question fully settled, I thought the 

 evidence against the volatile compound theory sufficiently good to 

 warrant the publication of the results thus far obtained. This I 

 was preparing for when notice of the preliminary paper f of Gosio 

 reached me. I wrote to Dr. Gosio at Rome, who after the com- 

 pletion of his work sent me, in September, 1892, copies of the two 

 monographs cited below, and at the same time, with the greatest 

 kindness and consideration, placed at my disposal an admirably pre- 

 pared set of tube cultures of Penicillium brevicaule. 



The Work op Gosio. 



Gosio's classic monograph % has received little attention from the 

 abstracters, and I therefore present his results here in considerable 

 detail. I judge that much of the work mentioned in my historical 

 sketch has escaped his notice, since he cites Selmi as the most reliable 

 authority for the volatile compound theory, and refers to the very 

 insufficient results of Forster as the basis for support of the dust 



* Estimated to be about 12,000 litres in 21 hours, from the statement of Fos- 

 ter, Textbook of Physiology, 5th ed., p. 551, that the amount of tidal air is 

 500 c.c., and that the number of respirations is 17 per minute. 



t Science, XIX. 104, abstract from a preliminary communication to the Con- 

 gress of Hygiene held in London in 1891. 



\ "Azione di Alcune Muffe sui Composti fissi d' Arsenico," Ministero dell' 

 Interno, Laboratori Scientifici delta Direzione di Sanita, Roma, 1892. 



