51 
Schaudinn® considers yeasts as normal commensals of all mosquitoes 
and believes they play an important part in the physiology of the 
insect, generating the gas that is almost always found in the eso¬ 
phageal diverticulum and also producing an enzyme or other irritat¬ 
ing substance which, when injected under the skin of man, causes the 
inflammation resulting from mosquito bites. Schaudinn considers 
these yeast cells to play a very important part in the economy of the 
insect and believes them to be hereditarily passed from the adult 
through the egg to the larvae and pupae. 
Mosquitoes fed upon fruits have many more yeast cells in their 
bodies than those fed upon blood or other material. This we were 
able to confirm. We also fed mosquitoes upon pure cultures of 
wild yeasts growing upon banana, and found that the insects fed on 
such a fermenting diet tvould soon be so swelled up with gas that 
their bodies looked like transparent air bubbles. Insects so fed do 
very badly and it is difficult to keep them alive over a week in trop¬ 
ical temperatures. 
Some of these wild yeasts are very interesting; one in particular— 
the Saccharomyces apiculatus , which is found widely spread through¬ 
out nature especially on fruit. This particular yeast assumes at times 
characteristic spindle or lemon shapes, with a bud at the pointed 
end, somewhat resembling one of the conjugating forms of protozoan 
organisms with which it has been confused. 
We were enabled to isolate this yeast in pure culture from the 
bananas at Vera Cruz only after some difficulty. The ordinary plate 
methods failed because the other saccharomyces overgrew the small 
colonies of S. apiculatus. The following expedient finally succeeded: 
The overripe and fermenting piece of banana containing the mor¬ 
phologic forms desired is planted into orange juice. This culture 
medium was made by simply squeezing the oranges, taking care not 
to get any of the oil of the peel, then filtering until clear, and steriliz¬ 
ing by heat in test tubes. As the Saccharomyces apiculatus is a bot¬ 
tom yeast, the growth which appears at the bottom of the test tube in 
twelve to eighteen hours is examined under the microscope and, if the 
proper forms are found, transferred to another tube containing 
orange juice. This is repeated until a number of subcultures are 
made, and as the Saccharomyces apiculatus grows better in the orange 
juice than the other yeasts, the latter are quickly left behind until 
a pure culture is obtained. 
We have noted in stained preparations of these wild yeasts that 
they sometimes show red chromatin (?) granules in a blue protoplasm 
a Schaudinn, Fritz 1904, Generations- und Wirtswechsel bei Trypanosoma und 
Spirochaete (vorlaufige Mitteilung.). Arb. a. d. k. Gesundbeitsamte, Berk, 4°. 
13046—05 M - 2 
