1 86 



THE ANIMAL PARASITES OF MAN 



within it the polar filament is differentiated ; the other forms the posterior vacuole 

 (fig- 98, g)> Between the two vacuoles the body cytoplasm or sporoplasm forms a 

 girdle-like mass. Of the nuclei, one regulates the polar capsule, two control the 

 secretion of the sporocyst, and two remain in the sporoplasm. The polar capsule and 

 polar filament are not usually visible in the fresh condition, but can be demonstrated 

 by the use of various chemical reagents (fig. 100). The sporoplasm ultimately becomes 

 the amcebula (fig. 98, g) which issues from the spore after the ejection of the polar 

 filament. 



A trophozoite (meront) of N. apis becomes a single pansporoblast which gives 

 rise to one sporoblast producing one spore, and this procedure is characteristic of 

 the genus Nosema. In other genera the trophozoite may form more than one pan- 

 sporoblast and each pansporoblast may form a variable number of spores in different 

 cases. Various attempts at classification have been based on these characteristics. 

 It must suffice here to note that in the cases where the trophozoite becomes one 

 pansporoblast, the latter can produce four spores in the genus Gurleya, eight spores- 



FIG. 99. a, section through the abdominal 

 wall of a silkworm, whose epithelial ceils 

 contain Micrusporidia (Nosema bombycis) ; l>, 

 a spore, the contents of which are escaping. 

 (After Balbiani.) 



FlG. IOO. Nosema bombycis, Naeg. 

 Spores treated with nitric aciri, thus 

 rendering the polar capsule perceptible, 

 and the filament has protruded from one 

 of the spores. (After Theluhan.) 



in Thelohania and many spores in Pleistophora. In other cases, where the tropho- 

 zoites give rise to many pansporoblasts, each of the latter may form many spores,, 

 as in the genus Glugea. 



A few pathogenic microsporidian parasites other than N. apis may be mentioned. 

 N. bombycis, causing pebrine in silkworms, may infect any or all the tissues of the 

 host (fig. 99). The larvas of the host i.e., the " silkworms," may become infected by 

 eating food contaminated with spore-containing excrement of already infected silk- 

 worms. In cases of heavy infection the silkworm dies, but should the infection be 

 less intense the larva becomes a pupa in which the parasite persists, so that the moth 

 emerges from the cocoon already infected. Not only is the moth parasitized itself, 

 but the Nosema reaches the generative organs of both sexes and penetrates the 

 ovaries of the female, with the result that the ova are deposited infected. Such 

 infected eggs are capable of developing, so that infection may be transmitted 

 hereditarily as well as by the contaminative method. Infected eggs can be recog- 

 nized by microscopic examination, as Pasteur showed, and thus preventive measures 

 may be adopted. 



A microsporidian parasite is known to occur on the roots of the spinal and cranial 

 nerves of Lophius piscatorius, the angler fish. This parasite is variously referred to 

 the genera Nosema and Glugea. 



Thelohania contejeani, parasitic in the muscles of crayfish, is believed by some 

 to be the causal agent of recent epizootics among them, though others believe the 

 disease to be really due to a bacillus. It may be that the one organism aids in the 

 entry of the other into the host. 



