532 MALARIAL FEVER 



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 hsemosiderin. 

 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 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 population, and 

 the killing of the larvae by petroleum sprinkled on the water, 

 have constituted one of the most important measures. This 

 procedure has been carried out in various places with marked 

 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 without becoming infected. The administration of 

 quinine to persons living in highly malarial regions, in order to 

 prevent infection, has also been recommended and carried out. 

 In the tropics the natives in large proportion suffer from malarial 

 infection, and one would accordingly expect that infection of the 

 mosquitoes in the neighbourhood of native settlements will be 

 common. This has been found to be actually the case, and it 

 has accordingly been suggested that the dwellings of whites 



