122 THE POPULAR SCIENCE MONTHLY 



with a specific disease of man was the ameba discovered by Lambl 

 (1860), first observed in the human intestine by Losch in 1875, and 

 said by the latter to be the cause of amebic dysentery. In 1891 Coun- 

 cilman and Lafleur, after a very accurate study of this disease, as it 

 occurred in Baltimore, came to the conclusion that two types of amebse 

 must be recognized ; one, the Ameba coli, was harmless, another, which 

 they called Ameba dysenteries, they claimed to be the cause of tropical 

 dysentery. In this view they were supported later by the feeding 

 experiments of Casagrandi and Barbagallo (1897) and of Schaudinn 

 (1903) ; the latter also introduced the name Entameba histolytica for 

 the pathogenic form, and Entameba coll for the harmless form. It has 

 since been found that two forms of tropical dysentery exist, one of 

 which, as shown by Shiga, Kruse and Flexner, is due to bacteria — but 

 equally definitely has the etiology of an amebic form been established. 



In the meantime another protozoan disease was being investigated. 

 Laveran, a French military physician, stationed in Algiers, announced 

 in 1880 that the dancing pigmented bodies frequently seen in the red 

 blood cells in malaria were altered hemoglobin granules within a pro- 

 tozoon to which he gave the name Oscillaria malaria;. This name was 

 altered by Marchiafava and Celli to Plasmodium malaria^, in 1885, and 

 Golgi, in 1886, by demonstrating that the characteristic paroxysms of 

 the disease coincide with the segmentation or sporulation of this para- 

 site, settled definitely the question of its etiologic relation to malaria. 



The work on malaria constituted a very large part of the activity in 

 medical investigation at this time. Until the middle of the nineties, 

 many investigators were interesting themselves in the study of the dif- 

 ferent forms of parasites concerned, their life history and the methods 

 for demonstrating them ; these activities, with the study of similar para- 

 sites in birds, gave a great impetus to the study of pathogenic protozoa, 

 and prepared many workers for a wider field. 



Nevertheless, but few were prepared for the wonderful announce- 

 ment by Smith and Kilbourne, in 1893, of the transmission of a proto- 

 zoan disease through a blood-sucking insect. In this, the work of our 

 own countrymen, on a malaria-like disease of cattle, Texas fever, the 

 tick was shown to be the carrier of the Pirosplasma bigeminum, the 

 organism responsible for the disease. The importance of this observa- 

 tion can not be over-estimated. It was the finger-post indicating the 

 way to progress in the study of the transmission, and therefore of the 

 prevention, of protozoan disease, and to Smith and Kilbourne belongs 

 the credit of this great advance, which, it must be admitted, had a great 

 influence on the study of the transmission of malaria and yellow fever. 

 Many suggestions had been made from time to time that these diseases 

 might be due to transmission by the mosquito; and these theories be- 

 came indisputable fact when Boss announced from India in 1897-99 



