SPOROZOA 775 



In quartan malaria the differences already described in stained 

 blood may be easily followed. 



In aestivo-autumnal fever the diagnosis with fresh blood is much 

 more difficult in new infections because of the relative scarcity of the 

 parasites in the peripheral blood and the exceedingly small size of the 

 young rings, the absence of hemozoin in them, and the very slight 

 ameboid motion. The older rings are larger, contain some pigment 

 and are more easily seen. The infected erythrocyte is never pale nor 

 swollen, but, on the contrary, may be shrunken and brassy in color. 

 The crescentic gametes are readily detected, and the sexes may be 

 differentiated by their shape and the hyaline or granular character 

 of the cytoplasm. 



Incubation Period of the Malarial Fevers. Two methods have 

 been used to determine this point the injection of infected malarial 

 blood, and biting experiments with infected anophelines. By the first 

 method the incubation period was eighteen days (the longest) for 

 quartan, three days (the shortest) for aestivo-autumnal, and ten days 

 for tertian. By the second method aBstivo-autumnal was nine to 

 twelve days, and tertian fourteen to nineteen days. Since aestivo- 

 autumnal is the only parasite which can complete its cycle in twenty- 

 four hours, the short incubation period is easily understood; on the 

 other hand, the long life cycle of quartan, seventy -two hours, explains 

 its slower development. 



Clinical descriptions of the malarial fevers may be found in the 

 standard text-books on medicine, and it is only necessary here to refer 

 briefly to the various forms found in practice. The classical malarial 

 fever consists of a series of paroxysms, following one another with a 

 definite periodicy, daily, every other day, or every third day. Each 

 paroxysm is ushered in by a pronounced chill, which is sometimes pre- 

 ceded by malaise, headache and lassitude. The chill lasts from ten 

 minutes to an hour or more, and the patient wraps himself up in 

 heavy blankets. During the chill the temperature begins to rise and 

 within a few hours reaches its high point, 103 to 106, and then 

 falls slowly to normal during the next few hours. The decline of the 

 fever is accompanied by a profuse perspiration. Successive parox- 

 ysms may occur at exactly the same hour of the day, or may antici- 

 pate, febris anteponens, or be delayed an hour or more, febris post- 

 ponens. The sequence of events, therefore, in a typical malarial 

 paroxysm is malaise, chill, "fever and sweat, followed by a period of 

 apparent well-being. 



