98 



A H.F.MOOKEOARINE OF MAMMALS 



Dimensions of 

 pamsitr 



ill tlif cast' of niiiliirial crescents. \Vlnii tlie reel cell is reco}j;iiisiil)le it is fouii<l to lie of a 



Very pale colour, iml 1 it looks as if no liicnioj^lohin were present in its spon^ioplasin. 'Die 



free forms. 1 ImIJcvi'. onvc their conilition to a total ilestniction or alisorptloii uf the suhstanee 

 of the ervthroeyles which once contained them. As .stated, the parasite is non-pigniented and 

 non-motile, and I have found it to lie rather resistant, remaining to all apjicarance miciianged 

 in sterile eitrated hlooil for a perio<l of seventy-two hours, hotli when kept at room 

 temperature (about 'Mi" C.) and at 22'' C. It is to he noted, however, that it altered 

 somewhat in its staining reactions. As a rule, it measures from HO to 7 f> in length, and 

 from 14 to 2H /I in breadtli. The number jiresent has been found to vary considerably. 

 There nmy be six or seven, or even more present in each mi<-roscopic field (Leitz oc. 4, oil 

 inna. ,'..th), or onlv a few may 1m- found in the wlmli- Mood smear. 



Appearanrr on 

 staining 



Diffcrrni 

 forms 



Staixino tiik Pahasite 



On staining by the lieishman-Romanowsky or the Gienisa niethoil in exactly the 

 same way as for malaria protozoa, the structure of the parasite becomes at once apparent 

 and tlie shape, as described above, well detined. (I'late XI., Fig. a.) A large oval nucleus, 

 constituting, as a rule, about one-third of the organism, is seen to be present, sittnited 

 generally in tin- cmtrc of tlic parasite and stntching right across it, so that there is a deep 

 blue staining area (the nucleus) in tiie middle, and a faintly staining blue area with a 

 rounded end on either side. Sometimes, but infrec|uently, forms with a ta|)ering doubled-over 

 end, i.i\, a "tail" flexeil on the body, can be demonstrated. (Plate XL, Fig. l>.) 

 Occasionally but lanly. and tlun nsnuiiy under special conditions, spherical chromatin 

 dots may be fouml in one or other of these pale polar areas. In stained preparations 

 one often notices that no vestige of the red blood corpuscle which originally harboured 

 the parasite remains, but it is quite common to find parasites with portions of the 

 red-staining erythrocyte adhering to them. All that may lie present is a thin. rid. 

 curved line stretching from pole to pole across the slight concavity of the parasite. The 

 corpuscles are often mucli deformed an<l take the eosin stain poorly. Sometimes, especially if 

 the blood be eitrated, the relation of the parasite to the blood cell which contains it is 

 beautifully shown. A process of absorption of the cytoplasm of the reil ct 11 evidently goes 

 on, and in a severe infection there must be a considerable destruction of erythrocytes. The 

 animal host, however, does not seem to suft'er in health. I have kept a jerboa with a 

 consiilerable infection for three months in the laboratory, and it renuiined well and lively 

 throughout the whole period. Three others dieij in captivity, exhibiting violent inih-mortiin 

 convulsions, and it is worth noting tiiat these rodents do nut staml handling w.ll anil 

 must not be supplied with water. 



In the peripheral blood it is customary to find all the parasites at or about the same 

 stage of development. Tnir. tiny ditl'ir sunicwhat in aspect. Thus it is not nnconnnon to 

 find the nucleus situated at one pole, so that half the parasite stains a deep blue and the 

 other half a very faint blue. Again, one end of the parasite may be pointed, so that the 

 body is club-shaped. This is |M-obably due to alteration during the |U-eparation of the blood 

 smears. In the heart's blood of a jerboa which died naturally I found two distinct forms, 

 a large swollen variety (11 2 ^ by 42 p), in which the greatest increase had taken place in 

 the light staining part of th<' protoplasm, ami a form like those already described. 

 It was very noticeable that the nm lei of the former, often of a triangular shape, stained a 



