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during the past year, viz. the part played by the mosquito in 

 connection with malarial fever. The chief difficulty which 

 is met with in many parts of the tropics lies in the attacks 

 of malaria which are suffered by nearly all the Europeans 

 who have to live there. 



For many years the cause of these attacks was attributed 

 to some state or other of the immediate surroundings — 

 miasma arising from the swamps, turning over or breaking 

 of new ground, as in making the canal at Panama, decom- 

 position of luxurious tropical vegetation, germs in the 

 drinking water, or some similar cause. Persons were spe- 

 cially liable to fever if they slept out at night, so the night air 

 was supposed to be especially hurtful. In extra-tropical 

 countries, such as Italy, residents during the summer months 

 were very liable to certain kinds of fevers, and these also 

 were considered as arising from the air (especially night air) 

 or the water. 



In the year 1880 Dr. Laveran discovered certain parasites 

 in the red corpuscles of patients suffering from malaria, and 

 he assigned to them the cause of the disorder. In 1885 

 Golgi established the fact that these parasites multiplied by 

 endogenous reproduction by means of spores, which give rise 

 to sporocytes. 



Later on several Italian observers noted that some of the 

 spores produced were crescentic in shape, but failed to 

 understand the nature and object of this kind. In 1894 Dr. 

 Manson, in this country, concluded that the function of these 

 particular spores was to continue the species outside the 

 vertebrate host, and that they escaped into the stomach of 

 a suctorial insect, where they developed into flagellulae, which 

 in turn developed in the tissues of the insect. Dr. Laveran 

 had already surmised that the mosquito is the alternative 

 host of the human parasite, and Manson now claimed the 

 mosquito as the suctorial insect referred to. By his sugges- 

 tion and advice Major Ross undertook an investigation of 

 the subject in India. 



In 1897, by the study of two species of the genus Ano- 

 pheles, Ross traced the malarial parasite into the walls of 

 the stomach of the mosquito after it had fed on malarial 

 patients whose blood contained the crescentic gametocytes. 

 Following this, Professor Grassi, in Italy, attacked the 

 problem from another direction : he studied the distribution 

 of the mosquito in different parts of the country where 

 malaria was common. He found that malaria was absent 

 where only Culex pipiens was present, but that it was rife 



