SPOROZOA 1115 



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 arc larger, contain some 

 pigment and are more easily seen. The infected crythrocyte is 

 never pale nor swollen, but, 011 the contrary, may be shrunken and 

 brassy in color. The crcscentic gametocytes 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 aestivo-autumnal was nine 

 to twelve days, tertian fourteen to .nineteen days, and quartan 

 eighteen to twenty-one 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 develop- 

 ment. 



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 an- 

 other with a definite periodicity, daily, every other day, or every 

 third day. Each paroxysm is ushered in by a pronounced chill, 

 which is sometimes preceded 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 tempera- 

 ture 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 per- 

 spiration. Successive paroxysms may occur at exactly the same 

 hour of the day, or may anticipate, febris anteponens, or be delayed 

 an hour or more, febris postponens. The sequence of events, therefore, 

 in a typical malarial paroxysm is malaise, chill, fever and sweat, 

 followed by a period of apparent well-being. 



There, is, of course, a typical symptomatology and clinical course 

 in the various forms of malarial fever, but it must not be forgotten 

 that there are many atypical cases, and that malaria is a protein 



