198 NATURAL SCIENCE. Sept.. 



fever in which, after one paroxysm, the next occurs on the fourth 

 day. If the blood of a patient be examined on the first day in a 

 case where the fever has a single origin, then only such forms 

 as those represented in Figs, a — c will be seen ; on the second 

 day will be found the forms with the larger hsematozoa — as 

 the parasites may be called — such as those shown in h and i. 

 During this period the patient does not suffer fever : if the disease be 

 of the intermittent type the temperature will be normal ; if remittent, 

 it will be a little above this point. Then, if the blood be watched, the 

 spore formation (Fig. k) is seen to commence, and the temperature of 

 the patient rises, probably by the secretion of some poisonous product 

 into the blood. The paroxysm of the fever, during which the 

 temperature may rise to io6° without serious danger, is always 

 approximately synchronous with the setting free of a fresh generation 

 of spores. 



Numerous deviations from this occur : thus some fevers are 

 quotidian and the haematozoa complete their life-cycle in one day, and 

 others are tertian with a 48 hours' cycle. Moreover, in any type, 

 many of the haematozoa do not complete their normal development. 

 The most important series of irregularities, however, is due to the 

 presence in the blood at the same time of more than one generation, 

 or more than one species of parasite. This is seen in Fig. I. Thus 

 in the lower part of the figure is a corpuscle with a haematozoon in the 

 earliest stage, while scattered over the field are several fully developed 

 and two which are undergoing spore formation. Owing to the 

 presence of this latter series the patient is either in or very near to a 

 paroxysm of fever. Twenty-four hours later the younger generation 

 will have reached the spore-forming stage, and thus another paroxysm 

 of fever will be brought about. Therefore, though the life-cycle of this 

 parasite takes two days for its completion, the patient will have a 

 daily attack of fever, as the two generations alternately reach the 

 spore-forming stage. 



Considerable difficulty has thus been introduced into the study of 

 these malarial diseases, owing to the complications caused by the 

 simultaneous presence of two or more generations of the same species 

 or even of altogether different species. 



This raises the question as to whether the various haematozoa are 

 defi.nite species or only forms of one or few species modified by 

 different conditions. This has given rise to great difference of 

 opinion. Laveran and his school maintain that there is but one 

 species and that all the varying forms are due only to polymorphism ; 

 thus Laveran sums it up in his great monograph (3), "Du paludisme 

 et de son hematozoaire," issued in i8gi, that " Le parasite est unique, 

 mais son evolution est variable." The Italian school, however, and 

 Dr. Mannaberg agrees with them, maintain the plurality of the 

 species ; Grassi and Feletti defined two genera, Lavevania and 

 Hamamceha, and numerous species, and these are now generally 



