IX] HISTORICAL 121 



announced the existence of a third species of parasite, charac- 

 terized by the occurrence of very minute forms, and now known 

 as the cestivo-autumnal, malignant tertian or tropical parasite. 

 It was shortly afterwards discovered that certain large and 

 peculiar crescentic forms of the parasite, now very familiar 

 as crescents, were a stage in the life-cycle of this third species. 

 In addition these and other Italian workers by their collective 

 researches made quite clear the real parasitic nature of Laveran's 

 bodies and by elaborating methods by which they could be 

 demonstrated, laid the foundation for the study of the malarial 

 parasite by observers in other parts of the world. 



In the decade or so following upon these early observations 

 a great many important facts in regard to malaria were elicited. 

 It was shewn that infection could be conveyed to healthy 

 persons by the subcutaneous or intravenous inoculation of the 

 blood of malarial subjects. It was also proved that in such 

 cases only that form of parasite appeared which had been 

 present in the original infection, thus greatly strengthening 

 the view of a plurality of species. Other species more or less 

 resembling the malarial parasite, but shewn to be distinct, were 

 also found to occur in birds, bats and other animals, and were 

 closely studied. Special methods of staining were elaborated 

 and much work was done with regard to the peculiar crescent 

 bodies and the process of exflagellation exhibited by these 

 and by certain other forms of the parasite. 



All efforts to discover how the parasites gained an entrance 

 to the blood of man, however, failed. Experiments (Marchia- 

 fava ; Celli, 1885 ; Marino, 1890, and Zeri, 1890, etc.), under- 

 taken with a view to producing malaria in healthy persons 

 by causing them to drink water from notoriously malarious 

 places, were without result. When marsh water was injected 

 into animals a condition thought at first to be malaria was 

 produced, associated with tumefaction of the spleen and the 

 appearance of pigment in the organs. But it is now obvious 

 that this condition was one of septicaemia, and with the dis- 

 covery of the malarial parasite any significance attaching to 

 these experiments had to be abandoned. 



The possibility that mosquitoes might be concerned in the 



