1921] Riley: Guide-posts to Medical Entomology 167 
as seen on the shores of the Red Sea. It has even been sug- 
gested that the fiery serpents which attacked the Israelites in 
the desert were guinea worms and that Moses set up the serpent 
on the stick as an illustration of the method of extraction. 
As is to be expected, many theories as to the origin of this 
famous parasite were proposed. Mercurialis, the Italian phy- 
sician who about 1590 so clearly outlined the theory of the 
carriage of contagion by flies, ventured again into medical 
entomology, when he suggested that the guinea worm was 
contracted from eating grasshoppers. Others believed it identical 
with the “Gordius aquaticus’’ or hair snake. It was often 
maintained that infection was conveyed through drinking 
water and probably many a traveler followed the example of 
Baron von Jacquin who declared ‘‘ Well, then, I’m safe enough 
for I shall not drink a drop of water.’’ We read that in spite of 
his self-denial he was the only one of his company who became 
infested. 
The prevailing view was that the Guinea worm, lying under 
the skin instead of in a cavity of the body, afforded conclusive 
proof of the origin of parasites within the host. 
In 1870 Fedschenko first found that if the larvee discharged 
by the parent worm escape into water they may be taken up 
by the little crustacean, Cyclops and within its body they 
develop to a certain stage. Man becomes infested by swallowing 
the Cyclops in drinking water. Since Fedschenko’s announce- 
ment there has been abundant verification. We can only con- 
clude that the Baron von Jacquin must have broken his pledge, 
for we have no evidence that Cyclops will thrive except in 
water. 
Among the worms found to require an arthropod as inter- 
mediate host were several species of thorn-headed worms. In 
1873 Leuckart showed that Echinorhynchus proteus and Echino- 
rhynchus angustatus of fish develop as larvee in two Crustaceans, 
respectively Gammarus pulex and Asellus aquaticus. One of 
this same group of worms which sometimes occurs in man was 
found by Grassi and Calandruccio, 1888, to develop in the 
meal infesting larva of Blaps. Still another, the largest of the 
group, develops in the larva of the June bug. 
Other instances might be cited, but it is not my purpose to 
make this a mere catalogue of the parasites which were early 
