n6 Insects and Disease 



man or any other animal they pour down through 

 the ducts with the secretion and are thus again in- 

 troduced in the circulation. 



The nodules or cysts on the walls of the stom- 

 ach of the mosquito may contain as many as ten 

 thousand sporozoites, and as many as five hundred 

 cysts may occur on a single stomach. 



It takes ten, twelve or more days from the time 

 the parasites are taken into the stomach of the 

 mosquito before they can go through their trans- 

 formations and reach the salivary gland, the time 

 depending on the temperature. So it is ten or 

 twelve days or sometimes as much as eighteen or 

 twenty days from the time an Anopheles bites a ma- 

 larial patient before it is dangerous or can spread 

 the disease. On the other hand, the sporozoites 

 may lie in the salivary gland alive and virulent for 

 several weeks. It does not give up all the para- 

 sites at one time, so that three or four or more 

 people may be affected by a single mosquito. 



It is well known that two parasites may often 

 be seen in the same corpuscle. This is often simply 

 a case of multiple infection, but Dr. Craig has very 

 recently shown that under certain conditions two 

 individuals may enter the same corpuscle and con- 

 jugate and the resulting individual will be resistant 

 to quinine and may remain latent in the spleen or 



