INSECTS IN RELATION TO OTHER ANIMALS 3OI 



The malaria "germ," discovered in 1880 by the l-rc-ncli 

 army surgeon Laveran, may be found as a pale, ama-bojd 

 organism (Plasmodium, Fig. 269) in the red blood corpus- 

 cles of persons afflicted with the disease. This organism 

 (scliirj'Jiit, 2) grows at the expense of the haemoglobin of the 

 corpuscle ( J~5) and its growth is accompanied by an increasing 

 deposit of black granules (melanin), which are doubtless 

 excretory in their nature. At length, the amcebula divides 

 into many spores (merosoites, 6) , which by the disintegration 

 of the corpuscle are set free in the plasma of the blood. Here 

 many if not most of the spores, and the pigment granules as 

 well, are attacked and absorbed by leucocytes, or white blood 

 corpuscles, while some of the spores may invade healthy red 

 corpuscles and develop as before. The period of sporulation, 

 as Golgi found, is coincident with that of the " chill " experi- 

 enced by the patient; and quinine is most effective when ad- 

 ministered just before the sporulation period. The destruc- 

 tion of red blood corpuscles explains the pallid, or anaemic, 

 condition which is characteristic of malarial patients. In 

 three or four days the number of red corpuscles may be re- 

 duced from 5,000,000 per cubic millimeter the normal num- 

 ber to 3,000,000; and in three or four weeks of intermittent 

 fever, even to 1,000,000. 



Three types of malaria are recognized : ( I ) the tertian, in 

 which the paroxysm recurs every two days; (2) the quartan, 

 in which it happens every third day; and (3) the sestivo- 

 autumnal type (Fig. 269). These three kinds are by some 



forming microgametes. qb, resting cell, bearing six flagellate microgametes (male). 

 10, fertilization of a macrogamete by a motile microgamete. The macrogamete next 

 becomes an ookinete. //. ookinete, or wandering cell, which penetrates into the wall 

 of the stomach of the mosquito. 12, ookinete in the outer region of the wall of the 

 stomach, i. e., next to the body cavity. 13, young oocyst, derived from the ookinete. 

 14, oocyst, containing sporoblasts, which are to develop into sporozoites. 15, older 

 oocyst. 16, mature oocyst, containing sporozoites, which are liberated into the body 

 cavity of the mosquito and carried along in the blood of the insect. 17, transverse 

 section of salivary gland of an Anopheles mosquito, showing sporozoites of the malaria 

 parasite in the gland cells surrounding the central canal. 



1-6 illustrate schizogony (asexual production of spores); 7-16, sporogony (sexual 

 production of spores). 



After GRASSI and LEUCKART, by permission of Dr. Carl Chun. 



