THE INFECTIOUS DISEASES. 283 



The details of the process of fertilization and the formation of the 

 sexual cells which are capable of carrying on the cycle in the mosquito 

 have been best observed in the aestivo-autumnal fevers, so that the stages 

 will be here described in connection with the development of the crescent 

 gametes. These crescents are formed chiefly in the bone marrow from 

 the small ovoid, intracellular bodies, which can early in their develop- 

 ment be distinguished from the ordinary amoeboid forms by their more 

 abundant coarse pigment and oval outline. 



The adult crescents are quite constantly present in well -developed 

 cases, and are often found in the blood after treatment with quinine has 

 caused the disappearance of the amoeboid bodies, the power of resisting 

 the action of drugs being much more marked in the crescents than in any 

 other form of the plasmodium. Two types may be distinguished, both 

 of which begin as small amoeboid forms and gradually mature into oval 

 or cresceutic organisms. One of these, the microgametocytes, or the cells 

 producing the male elements, develops and gives off the flagelluni 

 (niicrogarnetes) ; the other, the macroganietes (female elements), neither 

 form nor give off flagella. According to Marchiafava and Biguaini ' the 

 microgametocytes are distinguished from the macrogametes by the fact 

 that in the former (the male form) the pigment is gathered in a fairly 

 compact mass in the middle of the crescent, the chromatin is more abun- 

 dant, and the entire body stains faintly ; while in the female form, the pig- 

 ment surrounds the rather scanty nuclear chromatin in a ring form, the 

 cell body stains deeply, and no flagella are given off. The crescents in 

 the fresh blood show no amoeboid motion, and even the pigment is mo- 

 tionless. They are either crescentic in form with the pigment collected 

 at the centre, or they may be spindle-shaped with somewhat scattered 

 pigment, or finally short, thick ovoid bodies with pigment irregularly 

 scattered or more frequently gathered into a ring about the nucleus. 

 They are all contained in red blood cells (eudoglobular), the faint rem- 

 nant of the red cell often being seen as a delicate line stretching between 

 the two horns of the crescent. 



The formation of flagella (microgametes) -does not take place in 

 the circulating blood ; it begins only after the blood has remained on a 

 slide for a few minutes or has remained for some time in the stomach of 

 the mosquito. These flagella, usually about four in number, bud out 

 from the periphery of one of the microgametocytes, which has assumed 

 a spherical instead of a crescent shape, and grow to a length of three to 

 five times the diameter of the red cell. They are either pointed or bul- 

 bous at their extremities, or they present swellings at irregular intervals. 

 Their motion in warm-stage preparation is rather rapid, and they finally 

 become detached and move about free in the serum (Plate L, Figs. 45, 

 46, 47). The pigment during this process usually remains at the centre 

 of the spherical microgametocyte and is actively motile, but in prepara- 

 tions stained to show the nuclear chromatiu, the latter may be seen to 



1 Other observers claim that the pigment in the male forms is scattered throughout 

 the plasmodium. 



