107 



cases of yellow fever in order to determine a heavy infection. In our 

 work mother mosquito of Set 1 had three feedings of yellow fever 

 blood from two severe cases. 



Mother mosquito of Set 2 and that of Set 3 each had one feed of 

 yellow fever blood early in the disease. 



That the interval between the infecting feed and oviposition must 

 enter as an important element in the transmission of the infection 

 through the eggs to the progeny — if such transmission ever takes 

 place in yellow fever — must be evident. Marchoux and Simond do 

 not report clearly on this point;" they state simply that their mosquito 

 was 20 days old at the time of oviposition and that some time prior to 

 the laying it had been made to sting several cases of yellow fever, 



In our experiments the intervals were as follows: 



Set 1. 



Group I, mosquitoes Nbs. 1 and 2. — The eggs producing these mos- 

 quitoes were laid 13| days from the first, 11 k days from the second, 

 and about 2£ days after the third feed of yellow fever blood. 



Group ZTj mosquitoes Nos. 3 and 1±. — The eggs giving rise to this 

 group were laid 16 days from the first, 14 days from the second, and 

 about 5 days from the third feed of yellow fever blood. (Compare 

 footnote ( a ), page 106.) 



Set 2. 



Group I, mosquito No. 5. — The eggs giving rise to this group were 

 laid 15 days after one feed of yellow fever blood. 



Set 3. 



Group I, mosquito No. 6. — The eggs giving rise to this group were 

 laid 14 days after one feed of yellow fever blood. 



Groups IT, III, and IV, mosquitoes Nos. 7, 8, 9, 10, ,11, 12, 13, and 

 lip. — The eggs giving rise to these groups were laid 15 days after one 

 feed of yellow fever blood. 



Another important factor in the problem, and one to which Mar- 

 choux and Simond call attention, is the time needed by the hereditarily 

 infected mosquito to become infective. In their case this was twenty- 

 two days. In our work the inoculations were carried up to and 

 including at least the forty-ninth day, as shown in Table 1. 



<* See note " on' page. 106. 

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