51 



:haudinn 3 considers yeasts as normal commensals of all mosquitoes 



believes they play an important part in the physiology of the 

 ct, generating the gas that is almost always found in the eso- 

 ?eal diverticulum and also producing an enzyme or other irritat- 

 substance which, when injected under the skin of man, causes the 

 immation resulting from mosquito bites. Schaudinn considers 

 e yeast cells to play a very important part in the economy of the 

 ct and believes them to be hereditarily passed from the adult 

 'Ugh the egg to the larvae and pupae. 



.osquitoes fed upon fruits have many more yeast cells in their 

 es than those fed upon blood or other material. This we were 

 to confirm. We also fed mosquitoes upon pure cultures of 

 I yeasts growing upon banana, and found that the insects fed on 

 1 a fermenting diet would soon be so swelled up with gas that 

 r bodies looked like transparent air bubbles. Insects so fed do 

 r badly and it is difficult to keep them alive over a week in trop- 



temperatures. 



ome of these wild yeasts are very interesting ; one in particular — 

 Saccharomyces apiculatus, which is found widely spread through- 

 nature especially on fruit. This particular yeast assumes at times 

 racteristic spindle or lemon shapes, with a bud at the pointed 

 , somewhat resembling one of the conjugating forms of protozoan 

 misms with which it has been confused. 



fe were enabled to isolate, this yeast in pure culture from the 

 anas at Vera Cruz only after some difficulty. The ordinary plate 

 hods failed because the other saccharomyces overgrew the small 

 nies of S. apiculatus. The following expedient finally succeeded : 



overripe and fermenting piece of banana containing the mor- 

 Logic forms desired is planted into orange juice. This culture 

 ium was made by simply squeezing the oranges, taking care not 

 et any of the oil of the peel, then filtering until clear, and steriliz- 

 by heat in test tubes. As the Saccharomyces apiculatus is a bot- 



yeast, the groA¥th which appears at the bottom of the test tube in 

 Ive to eighteen hours is examined under the microscope and, if the 

 Der forms are found, transferred to another tube containing 

 lge juice. This is repeated until a number of subcultures are 

 le, and as the Saccharomyces apiculatus grows better in the orange 

 e than the other yeasts, the latter are quickly left behind until 

 ire culture is obtained. 



Te have noted in stained preparations of these wild yeasts that 

 ' sometimes show red chromatin ( ? ) granules in a blue protoplasm 



Schaudinn, Fritz 1904, Generations- und Wirtawechsel bei Trypanosoma und 

 ochaete (vorlaufige Mitteilung.). Arb. a. d. k. Gesundheitsamte, Berl., 4°. 



13046—05 m 2 



