MALAEIAL FEVEE. 521 



PROTOZOAL DISEASES. 



Malarial Fever. 



NATURE. — Formerly, malarial fever of man was regarded as a disease 

 produced by the bad air of certain unhealthy localities, such as swampy 

 ground in hot countries. Laveran was the first to demonstrate the fact that 

 the cause of this disease is a very low form of animal life (the Plasmodium 

 of Laveran) which occurs in different formg, and gains entrance into the 

 body by means of mosquitoes of the genus anopheles, that act as their 

 carriers. The malaria parasite is a protozoon, and not a Plasmodium, which 

 term, in this application, is incorrect, though sanctioned by use. 



This parasite, in the form of very minute needle-shaped organisms, is 

 injected into our blood along with the saliva of the mosquito, at the moment 

 this fly bites our skin. Each of these spores (to adopt Professor Lankester's 

 nomenclature) enters a red blood corpuscle, imdergoes a stage of develop- 

 ment (amoebula), and breaks up into numerous spherical spores (enhaemo- 

 spores) which enter the blood by the destruction of the red corpuscle. They 

 then invade and destroy other red corpuscles and, by their continued multi- 

 plicatiofi, infect the whole of the blood. Other stages of development take 

 place, until their final transformation in the blooa is attained. They are 

 then in a suitable state to be sucked up by mosquitoes, and after that Lakes 

 place, they arrive in the stomach of their carrier, undergo changes and 

 migrations, and at last gain access into the mosquito's salivary glands. 

 They are then ready to make a new invasion. We thus see that these 

 organisms are parasites of the mosquito, as well as of man ; and that a 

 human being who is suffering from malarial fever can infect the mosquitoes 

 of a place which had hitherto been free from that disease. In this way, 

 one human being can indirectly infect another human being. Direct in- 

 fection from one man to another man can be communicated only by inocula- 

 tion. Some mosquitoes have their regular meals, just after sunrise and 

 after sunset, which are consequently the times for specially avoiding these 

 insects. ' 



The constitutional disturbance is chiefly due to the destruction of the red 

 corpuscles and to toxins elaborated by these parasites. 



In malarial districts, many young children have malaria parasites in their 

 blood and have large spleens. The percentage of children with enlarged 

 spleens (known as spleen index) shows the intensity of malaria in a district. 

 As the native children get older, their blood is progressively less liable to 

 the infection, and in native adults the parasites are rarely found. Immunity 

 from malaria can therefore be acquired. 



There are several forms of malarial fever, of which intermittent fever 

 (ague) and remittent or continued fever are the most common. The re- 

 searches of Majors Walter Reed and Gorgas and other observers show that 

 a mosquito (ciilex fasciatus) is the transmitting agent of yellow fever. 



Sir P. Manson points out that the successive generations of the parasites 

 of intermittent fever tend to become simultaneously mature in the blood of 

 their human host, about the same time every day, every second day, or 

 every third day, according to their species. Thus, those which live for 24 

 hours, produce quotidian (daily) fever ; those which exist for 48 hours, 

 tertian fever ; and those whose cycle of development is 72 hours, quartan 



