MALARIAL PARASITOLOGY 508 



In the earlier stages they resemble the younger form except that the 

 pseudopodia appear to be exaggerated; besides there is a rapid dancing 

 of the pigment due to protoplasmic currents in the parasite. The infected 

 corpuscle is swollen and paler. Later the parasite occupies the greater 

 portion of the corpuscle, which is now more difficult to make out. The 

 pigment is still more evident, so that this form is therefore most readily 

 found. 



The anatomical changes which have been going on in the parasite 

 are best studied in properly stained smear preparations. They become 

 presently sufficiently distinct to be followed in the living parasite; the 

 pigment gathers more or less centrally into a compact mass, and a per- 

 ipheral notching indicates that the parasite is preparing to divide into a 

 number of segments; the number of segments varies even in perfectly 

 typical acute cases, but from twelve to twenty may be counted as soon 

 as the parasite has become fully mature. Suddenly these spheroidal 

 segments separate from each other; a corpuscular remnant and the 

 pigment float away and are ultimately carried to the spleen. Phago- 

 cytic cells ingest these pigment masses. The young parasites attach 

 themselves to red corpuscles as already stated. The mature tertian 

 parasite is usually larger than a red corpuscle. 



The varying number of segments is possibly accounted for by the 

 difference in size, age, and constitution of the infested corpuscles. Later, 

 when the blood may have formed antibodies, irregularities are still more 

 readily explained. If suitable smears are made from blood containing 

 such tertian organisms the life cycle can be studied much more closely. 



The making of these smears is a simple matter. There are the cover- 

 glass and the slide methods, both of which have their peculiar advan- 

 tages. To make a cover-glass preparation, two square, very thin, hence 

 flexible, cover-glasses are cleaned. Holding one with thumb and index 

 fingers by opposite corners the tip of a drop of blood obtained by needle 

 puncture of finger or lobe of ear is made to touch the centre of the cover- 

 glass, and the second clean cover-glass held similarly is allowed to fall 

 upon the first one in such a manner that the corners do not coincide. 

 The blood droplet spreads by capillarity into a thin film, which is a 

 sign to pull the two covers apart in the plane in which they lie; good 

 results depend upon cleanliness, rapidity, and success in sliding the 

 two covers apart. 



A simpler way is to polish two slides. The tip of the exuded blood 

 drop is made to touch one slide near one end and the edge of the second 

 slide held at an acute angle to the first one is made to bisect the drop, 

 which will spread at the point of contact by capillarity across the slide. 

 Upon pulling the second or spreading slide over the first slide, never 

 changing the angle and applying gentle pressure, a thin layer of blood 

 suitable for examination will be formed. A slide made in this manner 

 should be dried immediately by agitation in the air. It may then be 

 fixed and stained in various ways. I would recommend a modification 

 of a method devised by me in 1900, which is given here below, together 

 with some others. 



