'In tl is. connection Thayer and Ifewet ,..n ."Amer System of Prac. Med.," Malaria," Weleh and Thayer. vol. i, p. 29 say: "We hare been unable to trace length of the cycle of develop r..t, and me have been unable further t ante t more types of thelutoninal parasite depending t•thtr upc,n thP length of the cycle of de tr upon any other morpholog i or al differences. \Ve believe 11,- t the lengt1 of the eveIe varies greatly in different eases, lasting usually from tmenty-four hours, or even a little less, to forty-eight hours or more. After the infection is live days or a NVIA`k old cer tain of the organisms, instead of segment ing, pursue :t further growth, developing into the hyaline, refractive, ovoid, and ciescentic bodies." The contrary view, in favor of the di tuade by Marchiafava and Mg t:an:I, is held by Mannaberg (Mannaberg, P.S9t): Nothitagers Spec. Path. u. Titer., IL 2, T. 2, S. GS), who not only concurs itt the division of the festivo-autumnal parasite into qiiotidian and tertian, but further subdiddes the former into the pigmented quotidian parasite and the un pigmented quotidian parasite. JAMES C. WILSON and TIIOMAS G. AsirroN.] The xstivo-autumnal parasite possesses the distinctive characteristic of produc ing crescent-shaped bodies; hence Welch has proposed for it the name of Ilwma tozoon faleiparum. These bodies are not usually found in the blood until a case of festivo-autumnal fever has lasted for a week or more. Their development is now regarded as intraeorpuscular, and in the early stages of their evolution they are infrequently met with in the cir culating blood. In the spleen and bone marrow, however, particularly the latter, they are to be found in abundance. They are to be regarded as transformed from the intracorpuscular spherical or ganisms, and do not belong to the cycle of development as regularly performed by the parasite. Instead of being cres centic, these bodies may be oval or fusi form in outline, and, of whatever form, are always pigmented.
The young hyaline body of the festivo autumnal parasite is the smallest of the malarial parasites, and, while in its earliest stages it may not show much activity, in the course of its development it presents marked amceboid movements. It is to be observed in the red blood ' corpuscle during or shortly after the par oxysni, and is about one-sixth the diam eter of its host. The young parasite is distinct, and stands out in contrast to the surrounding structure of the blood corpuscle. This clear, hyaline ring is usually thicker at one portion of its cir cumference, and presents one or more central or eccentric shaded dots, through which may be seen the color of the red blood-corpuscle; these spots are sup posed by some to be nuclei.
With the development of the parasite amceboid movements become active and are frequently attended with the throw ing out of pseudopodia. Pigment-gran ules, at first very fine and dark brown in color, soon begin to appear toward the periphery of the parasite. These gran ules later increase in size and number; but it is distinctive of the 2estivo-au tumnal parasite that they are fine and relatively few in number and possess but little motion. With the approach of the paroxysm the parasite becomes quiescent and the pigment-granules collect at or near its centre. The parasite next enters upon the stage of sporulation, which is characterized by much greater irregular ity than the corresponding stage in the evolution of the other varieties of mala rial parasites. The number of spores is variable and may range from six to twenty or more.
The corpuscle enveloping the parasite may not show any change in appearance. Very frequently, however, it becomes shrunken and deformed and assumes a brassy color, with retraction of the hautio globin away from the periphery and its distribution around the parasite. The fully-developed parasite in the preseg menting stage is smaller than the guar tan and tertian parasites at a similar period of their evolution, and, as a rule, is not more than one-fourth or one-third the size of the red blood-corpuscle.
Fever of a quotidian or tertian type may result from mstivo-autumnal infec tion, and this association is to be ascribed to variations in the length of the cycle of development of the parasite rather than to infection with supposed special varie ties. As previously observed, however, Marchiafava and Bignami, Mannaberg, and others subdivide the parasite into quotidian and malignant tertian varie ties, the latter in contradistinction to the tertian parasite of the regular variety described by Golgi. Further, not all of the mstivo-autumnal parasites develop pigment-granules, and cases occur in which no pigmented bodies are to be ob served at any stage. This fact has led to the further subdivision of the so called quotidian 2stivo-autumnal para site into pigmented and unpigmented forms (Grassi and Feletti, Mannaberg). The following description is given by Mannaberg as distinctive of these varie ties:—