THE NATURAL HISTORY OF BOMBAY MALARIA. 393 



had mostly disappeared and small unpigmented parasites were 

 present in many of the corpuscles of the patient. Laveran de- 

 duced from these observations that the organism he had been 

 studying was the cause of malaria, and that the actual onset of an 

 attack of fever took place when large mature parasites were repro- 

 ducing themselves by a process of sub-division or shizogony. 



Several different forms of malarial fever have long been recog- 

 nised. The commonest is the so-called Tertian Ague, characterised 

 by recurring attacks of ague and fever every third da}^. That is to 

 say a man who had an attack on Monday might be quite free of 

 fever on Tuesday, but would have a recurrence of symptoms on 

 Wednesday and so on. Another form is Quartan Ague, in which 

 the attack occurring on one day would be followed by two days of 

 freedom from symptoms with a recurrence on the fourth day. 



A third and more severe kind of Malaria takes the form either 

 of a continued fever or a series of recurring paroxysms every third 

 day. In the latter form each paroxysm usually lasts for from 

 twenty-four to thirty-six or more hours, so that there is usually 

 only a short interval between them. This kind of Malaria is called 

 Malignant Tertian Fever. 



Since Laveran's original discovery of the malarial organism it 

 has been found that each of these types of Malaria is due to 

 a different species of parasite, and it has been definitely proved 

 that each phase of an attack of Malarial Fever is related to a corre- 

 sponding stage in the life-cycle of the organism associated with it. 

 For nearly twenty years after Laveran published his discovery 

 nothing was known as to the manner in which the parasite gained 

 entrance to the blood of man ; and though the life history of each 

 of its forms was carefully worked out by numerous observers, and 

 it was found that they could exist and continue reproducing them- 

 selves for long periods in the blood of infected persons, no one was 

 able to cultivate them or to keep them alive for more than a veiy 

 short time outside the human body ; neither had any one been able 

 to trace the presence of the organism in the air, the soil or the 

 water of malarious countries. But it had long been noticed 

 that among the parasites present in the blood of sufferers from 

 Malaria there were often large pigmented forms which were of a 



