526 APPENDIX C. 



accordingly the removal, where practicable, by drainage of such col- 

 lections 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 has been carried out recently 

 at Freetown by Logan Taylor, under the superintendence of Ross, and 

 the result has been to show that a marked lowering of the number of 

 cases may be effected at comparatively small cost. 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 have proved that 

 individuals using these means of protection may live in a highly malarial 

 district without becoming infected. The administration of quinine to 

 those 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 ex- 

 pect that infection of the mosquitoes in the neighbourhood of native settle- 

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

 it has accordingly been suggested that the dwellings of whites should as 

 far as possible be at some distance from the native centres of population. 



So far none of the lower animals have been found to act as inter- 

 mediate hosts to the parasite of human malaria, but the possibility of 

 such being the case cannot be as yet definitely excluded. On the death 

 of infected mosquitoes the exotospores or sporozoites will become set free, 

 and therefore theoretically there is a possibility that they may enter the 

 human subject by inhalation or by some other means. We have no 

 facts, however, to show that this really occurs, and the evidence already 

 obtained establishes the bites of mosquitoes as the most important if not 

 the only mode of infection. 



It may also be mentioned as a scientific fact of some interest, though 

 not bearing on the natural modes of infection, that the disease can also 

 be communicated from one person to another by injecting the blood 

 containing the parasites. Several experiments of this kind have been 

 performed (usually about \ to i c.c. of blood has been used), and the 

 result is more certain in intravenous than in subcutaneous injection. In 

 such cases there is an incubation period, usually of from seven to four- 

 teen days, after which the fever occurs. The bulk of evidence goes to 

 show that the same type of fever is reproduced as was present in the 

 patient from whom the blood was taken. 



Methods of Examination. The parasites may be studied by examin- 

 ing the blood in the fresh condition, or by permanent preparations. 

 In the former case, a slide and cover-glass having been thoroughly 

 cleaned, a small drop of blood from the finger or lobe of the ear is caught 

 by the cover-glass, and allowed to spread out between it and the slide. 



