288 THE AMERICAN MONTHLY [Oct 



were three species that found their home in the body of 

 men, two occurring in birds, one in monkeys, three in 

 bats, and perhaps some in frogs. These parasites, it was 

 found, inliabited at different times two very different hosts 

 — a discovery which would not have been expected, for 

 although it was known that the organism which caused 

 the Tsetze cattle fever was carried by insects, it was not 

 known that the organism actually lived in the body of the 

 insect. Major Ross described its method of reproduction 

 by division, and pointed out that in addition to this sim- 

 ple means of reproduction there was a much more com- 

 plex method of reproduction. At one stage in the devel- 

 opment of the organism there was produced a tiny thread, 

 which sprouted from the side of what was really the male 

 cell. The thread which he called a blastocyte was even- 

 tually cast loose and entered into another class of cell 

 which was really female, and there great numbers of simi- 

 lar threads were formed. At a certain stage this cell 

 burst and the threads were set free in the liquid blood of 

 the patient. It was the toxin which set up the fever, and 

 the moment of this breaking of the cells and the scatter- 

 ing of these threads was the moment of the setting in of 

 the fever. Then came the shivering, and subsequently 

 the sweating stage, at which the patient got rid of the tox- 

 in. The threads gave rise to spores, and the whole pro- 

 cess was gone through again. Hence arose the well-known 

 periodicity of malarial fever. If the finger of the patient 

 were j)ricked and blood drawn, the whole process of the 

 development of these creatures could be watched under 

 the microscope. 



If a mosquito bit a patient suffering from malaria fever 

 it sucked up into its stomach some of these blastocytes or 

 threads. These continued to multiply in the interior of 

 the stomach and accumulated in t he form of small cells ad- 

 joining the wall or the stomach, the membrane of which 

 was eventually penetrated by the cell, and the latter be- 



