APPENDIX. 333 



in perfectly^frcsh blood, but develop only after the blood has been drawn some 

 time, usually fifteen or twenty minutes. 



The extracellular forms of the parasite, the gametes, incapable of further 

 development in their human intermediate host, can continue their life cycle 

 only when, by chance, they happen to be sucked into the body of a mosquito 

 of the genus Anopheles, the definite host, in which they undergo a second com- 

 plete sexual cycle of development with the ultimate production of spores or 

 sporozoids. When in turn the spores chance to be inoculated into the blood 

 of man by the bite of an infected Anopheles, the man becomes infected, and 

 the cycle of development in the red corpuscle, already outlined, commences. 

 The second or sexual cycle of the parasite in the mosquito, here described 

 for the tertian organism, applies as well to the other varieties of the malarial 

 organism, namely the quartan and the estivo-autumnal forms, in the case of 

 each starting from the extracellular mature forms of the organism found in 

 the blood of the human host.* 



Quartan Parasite. — This resembles quite closely the ter- 

 tian parasite, but differs from it in certain respects. The 

 young, hyaKne, intracorpuscular parasite is more highly 

 refractive, its ameboid motion is less marked and more slug- 

 gish, and the pigment granules are darker, much coarser, 

 and have very slight motility. The infected red corpuscles 

 are usually somewhat contracted instead of swollen, and their 

 color is apt to be darker, assuming a bronzed hue. The 

 full-grown parasite is much smaller than the corresponding 

 form of the tertian, approximating the size of a normal red 

 corpuscle. As segmentation begins, a characteristic appear- 

 ance develops which distinguishes the quartan organism, 

 namely, the coarse pigment granules are drawn toward the 

 center of the parasite in certain converging straight paths, 

 giving a stellate arrangement to the pigment, until finally it 

 becomes clumped entirely at the center in a soKd mass. The 

 segmenting forms of the quartan parasite thus present a more 

 symmetrical arrangement of the spores, which often resemble 

 the petals of a "marguerite." These spores are oval and num- 

 ber only from, six to twelve, being fewer than those of the ter- 



* Lyon. The Inoculation of Malaria by the Mosquito. A Review of the 

 Literature. Medical Record. February 17, 1900. 



