ISZAS attnilnd LO the size of about one tb.r1 a the blood-corpuscle, the pig Lolleets in the middle or in that 1. .rt i•ii of the border where aruceboid mmements have ceased. Following the 1,14--in;_r of the pigment in this manner a dark, quiescent clump the para s.te reaks up into a limited number of small spores. Occasionally the or attains a considerable size and at the time of its sporulation may occupy alm,st the entire blood-corpuscle. It frequently happens, however, that the L-rpusele becomes shrunken and assumes a Lrassy hue. After the infection has .ntimied for a nmnber of days crescents are to l.e observed: these may be the or dinary creseentic-shaped bodies, the fusi frrrn bodies with pointed extremities, or the spherical bodies of this group.
PIP Unpigmented Quotidian Parasite. —The occurrence of a malarial parasite 71-at completes its cycle of existence, even sporulation, without accumulating pi;:rment has been described by :Afar -Ii:afava and Celli, whose observations I ave been confirmed by others. Except tlie absence of pigment, this parasite re-embles the pigmented quotidian para ,ite so closely that the same description may anzwer for both. In the early sta,e r.f exi:-tenee it possesses the same ,,m(.,boid movements and completes its cycle r.f development in about the same t:rne. er. perhaps, somewhat sooner. As in all frstivo-autumnal varieties, spor illation is carried on almost entirely in the internal org.ans. From this form of 1 parasite, also, crescents develop which, of course, contain pigment: a character istic common to all members of the cres centic group.
col ()RED PLATE IV.—Fig. A. 1-32. Ordi nary tertian parasite, show ing staining of its structure according to the method of Manna. berg (picric acid, lirematoxylin). Fig. B. Showing changes produced by the administra tion of quinine. Fig. C. 38. Cerebral capillary with pigmented parasites of the second group (from a preparation by Professor Celli). 39. Cerebral capillaries w ith unpigmented sporu luting parasites of the second group (from a , preparation by Professor Celli).
, The Malignant Tertian Parasite. — 1 This variety of parasite was separated 1 from the other forms by Marchiafava and Bignami. In its morphological char acteristics it resembles very closely the pigmented quotidian parasite from which in many stages of its development it is with difficulty differentiated. Marchi afava and Bignami claim for it the fol lowing points of dissimilarity: 1. Its cycle of development continues forty eight hours. 2. The pigment sometimes shows oscillatory movements, which do not occur in the quotidian parasite. 3. The parasite attains a considerable size and at the time of sporulation occupies one-half or two-thirds of the blood-cor puscle. 4. In the advanced stages of pigmentation active amceboid movements are still to be seen. 5. The unpigmented stage lasts over twenty-four hours.
From the ordinary tertian parasite the malignant tertian parasite differs in the following particulars: 1. In all stages the malignant tertian parasite is smaller. 2. It often assumes the distinct ring shape which the ordinary tertian para site lacks. 3. Pigment-granules are not so numerous and only exceptionally show motion. 4. The infected blood-corpus cles show a tendency to shrink, while in the ordinary tertian infection they swell I up. 5. The spores are smaller and not so numerous. 6. The pernicious tertian parasite develops crescents.
Degenerate forms of the a3stivo-au tumnal parasite, hydropic, fragmented, flagellate, or vacuolated, occur as in the other forms of malarial infection. These are derived from those parasites that fail to properly mature and undergo seg mentation, particularly the extracorpus cular bodies which in this variety of in fection are common.
Infection with two or more groups of mstivo-autumnal parasites, each in a dif ferent stage of development, is of com mon occurrence, and a combined infec tion with one of the other varieties, es pecially the tertian, is occasionally seen.