140 PROCEEDINGS OF THE AMERICAN ACADEMY. 



of Gosio, using the material from the culture tubes sent me by him, 

 which were five in number and contained P. brevicaule in potato 

 strips to which had been added different preparations of arsenic. 



Second Series of Experiments, using P. brevicaule. 



Experiment 15. — One gram arsenious oxide was mixed in a litre 

 flask with flour and water which, without sterilization, was inoculated 

 from the tube marked " patata esente di arsenico." A similar system 

 of tubes to that described in Exp. 3 was attached to this flask, including 

 the usual absorption bottles filled with 2% argentic nitrate, and air was 

 drawn through the system for about two weeks, during which time the 

 formation of mould was abundant and fermentation marked. The 

 reduction of the silver solution was slight. On opening the flask no 

 odor was noticed except that characteristic of mould. Although there 

 was little evidence of the formation of a volatile compound, the silver 

 solution was tested in a similar manner to that described in Exp. 1, 

 but with entirely negative result. 



Experiment 16. — One gram arsenious oxide was mixed with un- 

 sterilized flour paste, and, after inoculation with the same preparation 

 as in Exp. 15, smeared on a large sheet of filter paper. This was 

 placed in a bell jar over a ground-glass plate, and the jar fitted with 

 a system of tubes and absorbents similar to that described in Exp. 4. 

 Air was drawn through for about two weeks. The formation of 

 mould was abundant, but no alliaceous odor was observed. The sil- 

 ver solution was but slightly reduced and gave no test for arsenic. 



In these two experiments, the P. brevicaule could not tolerate the 

 amount of arsenic under the conditions as well as the common moulds, 

 hence the latter flourished to the entire exclusion of the former. 

 This was shown by Mr. Roscoe Pound, of Lincoln, Nebraska, who 

 very kindly examined the sheet in Exp. 16 and found the only 

 Penicillium present to be P. crustaceum. 



The conditions of Exps. 15 and 16 are not unlike those of the 

 previous negative experiments. 



Experiment 17 a. — In this the method of Gosio was .quite closely 

 followed. Three 250 c. c. Erlenmeyer flasks were fitted with rubber 

 stoppers through which passed two right-angled tubes, one reaching 

 nearly to the bottom of the flask, the other to just below the cork. 

 The outer end of each tube was plugged with cotton wool. Sufficient 

 potato pulp was placed in each flask to make a layer of about half an 

 inch, and it was moistened with a solution of sodic arseniate contain- 

 ing about 0.5 gram to 100 c. c. Each flask contained about 100 mgr. 



