I QO CLINICAL BACTERIOLOGY AND H^MATOLOGY 



immersion lens. The parasites are seen as pale, irregularly 

 shaped bodies with indistinct margins, which occupy the in- 

 terior of the red corpuscles, and show amoeboid movements of 

 greater or less rapidity. When the parasites are older they 

 occupy a larger space in the corpuscles, and there are granules 

 of dark pigment around their periphery. These granules are 

 often the first indications of the presence of parasites in the 

 examination of an unstained specimen. At a still later stage 

 the granules will be found in the centre of the corpuscles (the 

 haemoglobin of which is now almost entirely removed), and 

 the parasite will show segmentation into a larger or smaller 

 number of spores by lines which have a radial arrangement 

 and give the whole an appearance resembling that of a mar- 

 guerite daisy. These are only found when a rig'or is imminent. 



Crescents are found in the asstivo-autumnal form of malaria ; 

 they are crescentic bodies w T ith rounded " horns," and contain 

 a ring of pigment granules in the centre. They cannot be mis- 

 taken for anything else, and if a single one is found it affords 

 conclusive proof that the patient has been infected with 

 malaria. 



Films for staining are made in the ways already described, 

 and must be thin and perfect. They may be fixed by any of 

 the methods we have recommended, the alcohol-ether and the 

 alcohol-formalin methods being perhaps the best. They may 

 be stained by Jenner's stain, or by eosin and methylene blue 

 used separately; the parasites are stained pale blue and the 

 corpuscles bright red. 



ROMANOWSKY'S STAINS AND THEIR VARIETIES (WRIGHT'S, 

 LEISHMANN'S, ETC.). 



When methylene blue is digested with alkalies or alkaline carbon- 

 ates, a series of new compounds is formed. These substances arc 

 basic, having a special affinity for chromatin, and in particular that 

 of the protozoa, which they stain a brilliant red, whilst the nuclei of 

 the leucocytes, etc., are stained blue by the methylene blue remaining 

 unaltered in the stain. They are usually used in combination with 

 eosin, made similarly to Jenner's stain, but with methylene blue that 

 has been digested with sodium carbonate. Their preparation is diffi- 

 cult, and it is advisable to purchase them ready made, or to buy 

 tabloids or powders and dissolve them in pure methyl alcohol when 

 required. 



Leishmann's stain is used especially for blood films to demonstrate 



