424 MICROBIOLOGY 



if the animal was believed from its action to have had rabies, 

 the persons bitten should be warned of their possible danger, 

 in order that they may take the preventive treatment if they 

 so desire. 



SARCOSPOBIDIA. 



Place in nature. This order of protozoa is very little 

 inown. The sarcosporidia are parasites found in the striped 

 muscle and in connective tissue of certain mammals and birds. 

 The parasite belonging to this order appears, according to 

 ^Calkins, 1 in its earliest stages as a minute white body em- 

 bedded in the material of a muscle fiber, in which condition it 

 is known as Miescher's tube, a name applied to the vegetative 

 forms of the mouse parasite Sarcocystis muris. As the young 

 trophozites grow, the nuclei increase in number, a definite sac- 

 like membrane develops around the protoplasmic body, while 

 in the centre groups of spores begin to form. The ripening 

 spores (merozoites, gymnospores) gradually encroach upon 

 the more peripheral unused protoplasm of the tube until the 

 ^ends only appear to be active, and capable of vegetative func- 

 tioning, and even these, finally, are used in spore formation. 

 In Sarcocystis tenella of sheep such cysts may grow to a 

 length of two inches in the muscle bundles, where they ulti- 

 mately burst, the spores being scattered or carried by blood 

 to new regions, where development begins anew (auto-infec- 

 tion). In some cases the entire body may be overrun by such 

 parasites, mice especially often being killed in this manner. 



In all cases there is every reason to believe that this 

 method of endogenous multiplication can not be continued 

 indefinitely any more than a paramecium can continue to 

 divide indefinitely, and there is reason to suppose that the 

 potential part of vitality gives out at the end of a more or less 

 definite cycle of generations. In many cases, the organisms 

 seem to have devised a means of counteracting this senile 

 process and of being stimulated to renewed activity in much 



Calkins. Protozoology, p. 185. 



