powder resembling arsenic — however this may be, the larvae must 

 either instinctively reject the poison, or it is excreted by them 

 after ingestion. A number of these chrysalids were kept, in order 

 to ascertain if they would undergo metamorphosis, and, if so, 

 whether the perfect insects would be healthy and vigorous ; some 

 were kept two months, at the end of which time they were acci- 

 dentally lost, undergoing no change, remaining however in a per- 

 fect state of preservation and full of pulp ; a number of small 

 flies, apparently not ichneumons, which gained access to them, 

 died almost immediately, as was supposed from having fed upon 

 them — the empty shells of other chrysalids found about the room 

 showed that some had been metamorphosed, as none but the arsen- 

 ically-fed larvae had been admitted to the apartment. Experi- 

 ments made to determine how large a quantity of arsenic might 

 be contained in flesh without rendering it unfit for the food of 

 these larvae, were not very satisfactory, from the hardening of the 

 tissue by solutions of this substance preventing the deposition of 

 the eggs ; eggs develoj)ed in such tissue bring forth living w^orms, 

 which in his experiments died in six or eight hours. The adult 

 flies perished in great numbers, while depositing the eggs upon 

 the poisoned flesh. Jaeger (quoted by Orfila, Toxicologic I. 

 379) alludes to the fact that larvae of flies live a little longer than 

 the perfect insects, when arsenious acid is introduced into the 

 digestive organs or applied to their external soft parts. Under 

 favorable moist conditions, the larvae lived three or four days, and 

 were evidently nearly ready to pass into the chrysalid state. Ex- 

 periments with arsenic acid, used however in too concentrated a 

 state, also showed that there is a limit to the amount of arsenic 

 which these larvae can support. 



He was inclined to believe that they can eat with impunity any 

 flesh into which arsenic has been carried by vital processes, from 

 the fact of their being found upon the arsenicated liver, an organ 

 capable of absorbing a very large quantity of this poison ; ana- 

 tomical preparations, injected thoroughly with arsenic acid, have 

 been found completely riddled and alive with larvae. 



This matter is important to chemists occupied in judicial inves- 

 tigations, who should not infer that a fly-blown organ can contain 

 no arsenic ; though if flies die almost immediately after alighting 

 on a suspected substance, arsenic is probably present, and should 



