February, '13] BRUES: STABLE FLY AND INFANTILE PARALYSIS 107 



this period, as well as later, after paralysis had set in. This usually 

 appears on the fourth or fifth- day, and death ensues several days later. 

 Alternating with the inoculated monkey, healthy monkeys were simi- 

 larly introduced into the cage at intervals. In this way new monkeys 

 were inoculated to keep a supply of such infected animals and addi- 

 tional healthy ones were exposed to the flies, which fed willingly and 

 in considernble numbers on each occasion. Thus the flies were given 

 every opportunity to "obtain infection from the monkeys, since the 

 animals were bitten during practically every stage of the disease 

 from the time of the inoculation of the virus till their death following 

 the appearance of paralysis. By the same arrangement the healthy 

 monkeys were likely to be bitten by flies that had previously fed during 

 the various stages of the disease on the infected monkeys. The flies 

 had meanwhile enjoyed the opportunity of incubating the virus for 

 periods varying from the day or two which usually elapses between 

 consecutive feedings, to the two- or three-week period for which 

 at least some (although a very small percentage) of the flies lived in 

 the cage. 



At this point it should be mentioned that no fear was to be enter- 

 tained that the healthy monkeys might become infected on account 

 of their being introduced into the cage in which the poliomyelitic 

 animals had been placed. Attempts to transfer the disease under con- 

 ditions of far more intimate nature have been made, but have always 

 given negative results. 



In all, twelve apparently healthy monkeys of a small Javan species 

 were exposed to the flies in the manner described for the infected mon- 

 keys. Some were placed in the cage only once or twice, and others 

 a number of times after varying intervals. These exposures usually 

 lasted for about half an hour, but were sometimes more protracted. 

 No results were apparent until two or three weeks after the experiment 

 was well under way, and then in rather rapid succession six of the 

 animals developed symptoms of poliomyelitis. In three, the disease 

 appeared in a virulent form, resulting in death, while the other three 

 experienced transient tremblings, diarrhoea, partial paralysis and 

 recovery. It is interesting to note that several of the monkeys had 

 diarrhoea, wherein their affection resembled the human disease more 

 closely than the type developed in monkeys after inoculation with 

 virus in the brain, for gastro-intestinal upsets in children are frequently 

 associated with infantile paralysis. 



In support of the clinical appearance of the disease in the fly-bitten 

 monkeys, microscopic examination of the spinal cord revealed the 

 characteristic lesions of poliomyelitis, but we were unable to induce 

 the disease in further monkeys by intracerebral inoculations with 



