THE MALARIA-GERM. 189 



THE MALARIA-GERM AND ALLIED FORMS OF SPOROZOA. 



By Dr. GARY N. CALKINS, 



COLUMBIA UNIVERSITY. 



THE group of animal parasites to which the malaria-causing organism 

 belongs is relativeh' unimportant when compared with the bacte- 

 ria, a group of plant parasites, including the causes of most zymotic dis- 

 eases in man — typlioid, cholera, diphtheria, scarlet fever, tuberculosis 

 and the like, as well as beneficial forms which aid man in various 

 ways. Nevertheless, it is a group of considerable economic importance, 

 about which little is known outside of scientific circles. The name 

 Sporozoa suggests, to the average reader, no disquieting apprehension 

 of physical pain or of financial loss, yet this class of primitive, 

 unicellular animals includes, besides the malaria-causing blood para- 

 sites, forms which, like the silkworm parasite (Glugea hombycis), have 

 cost communities untold millions of dollars. In connection with the 

 losses due to one of these silkworm epidemics, Huxley writes in 18.0: 



" In the years following 1853 this malady broke out with such extreme 

 violence that, in 1853, the silk crop was reduced to a third of the amount 

 which it had reached in 1853; and up till within the last year or two it lias 

 never attained half the yield of 1853. This means not only that the great 

 number of people engaged in silk growing are some thirty millions sterling 

 poorer than they might have been; it means not only that high prices have had 

 to be paid for imported silkworm eggs, and that, after investing his money in 

 them, in paying for mulberry leaves and for attendance, the cultivator has con- 

 stantly seen his silkworms perish and himself plunged in ruin; but it means 

 that the looms of Lyons have lacked employment, and that, for years, enforced 

 idleness and misery have been the portion of a vast population which, in 

 former days, was industrious and well to do." 



Analogous epidemics, which may be traced to Sporozoa, are liable 

 to break out at any time among other animals having commercial value. 

 Thus 'Texas fever,' a cattle disease due to a sporozoan blood parasite 

 (Piroplasma higeminiim), occasions great loss to cattle breeders. Muscle 

 parasites, belonging to the same class, cause trichinosis-like diseases in 

 hogs, cows, cats, dogs and other domestic animals; while in fish they 

 occasion great loss to fish-culturists through epidemics. Other par- 

 asites in the same class are the causes of disease in horses, sheep, goats, 

 etc. 



The Sporozoa are comparatively harmless to man personally, but, 

 unlike some bacteria, they are never beneficial in any sense. Invariably 

 parasites, the diseases which they induce are confined mainly to the 

 lower animals, but so widely are they distributed that no type of ani- 

 mals is free from them altogether. One significant feature about the 



