596 MALARIAL FEVER 



cases with coma the cerebral capillaries appear to be almost 

 filled with them, many parasites being in process of sporulation ; 

 and in so-called algid cases, characterised by great collapse, a 

 similar condition has been found in the capillaries of the 

 omentum and intestines. The process of blood destruction, 

 present in all malarial fevers, reaches its maximum in the 

 malignant class, and the brown or black pigment elaborated by 

 the parasites in part after being taken up by leucocytes, chiefly 

 of the mononuclear class becomes deposited in various organs, 

 spleen, liver, brain, etc., especially in the endothelium of 

 vessels and the perivascular lymphatics. In the severer forms 

 also brownish yellow pigment is apparently derived from liberated 

 haemoglobin, and accumulates in various parts, especially in the 

 liver cells ; most of this latter gives the reaction of haemosiderin. 

 General Considerations. The development of the malarial 

 parasites in the mosquito and infection of the human subject 

 through the bites of this insect, have, by the work of Ross and 

 others, as detailed above, become established scientific facts. 

 These facts, moreover, point to certain definite methods of pre- 

 vention of infection, which have to a certain extent already been 

 practically tested. The extensive observations recently carried 

 out go to show that all the mosquitoes which act as hosts of the 

 parasite belong to the genus anopheles ; of these there are a 

 large number of species, and in at least eight or nine the 

 parasite has been found. Some of these anopheles occur in 

 England, especially in regions where malaria formerly prevailed. 

 The opportunity for infection from cases of malaria returning 

 from the tropics to this country thus exists, and such infection 

 has occurred. The breeding places of the insects are chiefly, 

 though not exclusively, in stagnant pools and other collections 

 of standing water, and accordingly the removal, where practicable, 

 by drainage of such collections in the vicinity of centres of popu- 

 lation, the covering in of wells, etc., and the killing of the larvae 

 by petroleum sprinkled on the water, have constituted the most 

 important measures in localised areas. This procedure has been 

 carried out in various places, for example, in Freetown and 

 Ismailia, with marked success. On the other hand, where there 

 are large populous areas, as in India, it has been found almost 

 impracticable to carry out these measures with any success,. 

 Another measure is the protection against mosquito bites by 

 netting, it being fortunately the habit of the anopheles to rarely 

 become active before sundown. The experiments of Sambon 

 and Low in the Campagna proved that individuals using these 

 means of protection may live in a highly malarial district with- 



