664 INFECTION AND IMMUNITY. 



lysis is entirely obscure; the effect is that of an 

 intense intoxication, in which the erythrocytes 

 suffer primarily and chiefly. Craig warns against 

 the administration of one large dose of quinin in 

 the 24 hours in asstivo-autumnal fever lest perni- 

 cious symptoms develop. 



The essential epidemiologic features of malaria 

 >gr> ' are the following : It prevails especially in tropical 

 and subtropical zones and less in temperate zones. 

 It is most abundant in low, swampy regions, and 

 in other places which afford quiet streams, ponds 

 or other standing water. It is not directly conta- 

 gious. In order to become infected it is necessary, 

 customarily, to enter or be in close proximity to a 

 "malarial district." That the virus is not carried 

 far from an infected district is shown by the 

 exemption of crews of vessels which lie within two 

 or three miles of such a district. Infection has 

 long been supposed to take place chiefly by night. 

 The disease may be introduced into new regions 

 (of suitable climate) by the importation of mala- 

 rial subjects. These and other phenomena of mala- 

 ria which were once very obscure have been cleared 

 Anopheles. u p by the mosquito theory. There are many spe- 

 cies of anopheles and they are distributed through- 

 out the world in warm and moderate climates. 

 Anopheles maculipennis is the most numerous spe- 

 cies, and for it, as well as for Anopheles puncti- 

 pennis, Howard has found several natural breeding 

 places in this country. It is probable that many, 

 but not all, species of anopheles may transmit 

 malaria. The female only is a blood-sucker, the 

 male living on vegetable material exclusively. 

 After the female has obtained blood from man or 



