118 
Tlieileria parva 
results. The minute intracorpuscular parasites in wet-fixed films are 
only seen indistinctly owing to the intervening cloudy layer of stained 
haemoglobin in the corpuscles, which do not assume the flattened shape 
observed in ordinary films. Wet fixation was tried in various ways, by 
osmic acid vapour, by sublimate-alcohol, by Flemming’s solution followed 
by staining with Delafield’s liaematoxylin, thionin, or safranin-methylene 
blue, etc., but the results were uniformly unsatisfactory. 
The morphology of the parasites as observed in stained preparations. 
The parasites vary much in size and shape, as will be readily seen 
by a glance at Plate XII. Parasites occurring singly in corpuscles may 
be of all shapes and sizes. When two parasites are contained in a 
corpuscle they may possess about the same shape and size (figs. 25, 26), 
but as a rule they differ considerably in both respects (figs. 21—24). 
This variation in size and form is very noticeable in corpuscles which 
contain larger numbers of parasites (figs. 31—45). Ovoid and bacilliform 
parasites (figs. 34, 36), or ovoid and comma-shaped parasites (figs. 32, 33), 
or, again, a cross-form, a bacilliform and a rounded parasite (fig. 48), etc., 
may be contained in one and the same corpuscle. 
We append some measurements made on typical specimens of the 
parasites in well-stained preparations : 
Ovoid parasites 1 to 1‘5 x 0'55 to 0’8 g. 
Rounded „ 1*5 to 17 x PI to P4 g. 
Comma-like „ 2 x 0‘7 g. 
Bacilliform „ 0'7 to 2’9 x 0'3 to 04 g. 
Although the shape of the parasites is very variable the commonest 
form is usually ovoid or oval (PI. XII, figs. 1, 2). In typical parasites 
belonging to this category the chromatin mass occurs at one pole along¬ 
side of a clear area in the blue-staining protoplasm which appears 
condensed peripherally. This clear area may represent either a vacuole 
or tenuous protoplasm. Rounded or ovoid parasites , often of larger size 
than the foregoing (figs. 9, 24, 36), are not infrequently encountered 
with a clear central area and a crescentic or horse-shoe-shaped mass of 
chromatin situated at one pole, its curvature corresponding to that of the 
external contour of the parasite. Some of the horse-shoe-shaped masses 
of chromatin (figs. 10, 34, 35, 42, 48) present a bent dumb-bell-like 
appearance through concentration of the chromatin distally, the appear¬ 
ance suggesting that they are undergoing division. In other cases 
