SPECIAL TOXICOLOGICAL TESTS 269 



Fruits and vegetables which have been sprayed with arsenical 

 compounds for the purpose of destroying insect pests, may contain 

 enough of this substance to produce symptoms of poisoning. 

 Arsenic is occasionally added to alcoholic beverages to give them a 

 tonic effect. It has been demonstrated that very minute amounts 

 of arsenic are normally present in various organs of the human 

 body, as the thyroid gland, thymus gland and liver, although 

 some investigators question the correctness of this claim. However 

 these somewhat problematical traces of arsenic in organs of the 

 human body and also in the organs of other animals need not 

 concern the food and drug analyst as far as routine work is 

 concerned. 



As a rule, the tests for arsenic outlined in the majority of text- 

 books are chemical and hence this work is usually relegated to the 

 chemical laboratory. Within recent years attempts have been 

 made to employ biological tests for determining the presence of 

 arsenic in food substances, based upon the discovery that certain 

 molds when growing in substances containing arsenic will give rise 

 to garlic-like odors. 



Gosio demonstrated that certain molds which when grown in 

 and upon media containing very minute quantities of arsenic 

 gave rise to gaseous compounds characterized by a garlic-like 

 odor. Seven different kinds of molds have this power, more 

 especially Penicillium brevicaule, which Gosio isolated from air 

 and which he frequently found on decomposing paper. Crumbs 

 of bread (wheaten) form the culture medium for this mold and 

 the incubation is done at 28° to 32° C, a vigorous growth being 

 produced within 48 hr. In the presence of not more than 

 o.ooooi gram of arsenic in such culture there will be noticeable 

 a distinct and very characteristic garlicky odor which may persist 

 for months, if the culture is not killed. These arsenic molds 

 do not produce garlic odors or gases with sulphur, phosphorus, 

 antimony, boron, and bismuth compounds but they do have the 

 power of converting selenium and tellurium compounds into 



