636 POPULAR SCIENCE MONTHLY. 



In the quartan type the red blood- corpuscles containing the 

 parasite have a tendency to become smaller than normal corpus- 

 cles ; in the tertian type they are usually larger. 



In the tertian the protoplasm of the parasites is very trans- 

 parent ; in the quartan it is less so, and the outlines are better 

 defined. 



In the quartan the pigment is seen in the form of grains or 

 rods of greater size than in the tertian. 



Finally, the principal difference is found in the segmentation 

 of the intracorpuscular elements. The number of spores result- 

 ing from segmentation is greater in the tertian parasite usually 

 more than twice as many. 



That these parasitic protozoa are in truth the cause of the 

 forms of malarial fever with which they are found to be asso- 

 ciated can scarcely be doubted, in view of the facts that this asso- 

 ciation is a constant phenomenon, that the infected blood- cor- 

 puscles are destroyed by the parasite, that a rapid loss of red 

 corpuscles is one of the most marked results of malarial infection, 

 and that the parasites disappear when quinine is administered in 

 suitable doses, thus accounting for the specific action of this drug. 

 Finally, it has been shown by inoculation experiments that when 

 blood containing the plasmodium is drawn from the circulation 

 of a malarial-fever patient and injected beneath the skin of a 

 healthy person there is a reproduction of the parasite in the blood 

 of the inoculated individual, and, after a certain period .of in- 

 cubation, typical malarial paroxysms occur. Successful inocula- 

 tion experiments have been made by Marchiafava and Celli, by 

 Gualdi and Antolisei, by Bein, by Bacelli, by Di Mattel, and 

 others. 



The life-history of the malarial parasite outside of the bodies 

 of infected individuals has not been traced. Thus far attempts to 

 cultivate it in artificial media have failed. Nor has the presence 

 of the Plasmodium been demonstrated in water or mud taken 

 from the marshy localities which are recognized as the source of 

 malarial fevers, and which we therefore believe to be the normal 

 habitat of this mischievous micro-organism. The facts relating 

 to the seasonal and regional occurrence of malarial fevers sustain 

 the view that they are caused by living organisms, the external 

 development of which depends upon conditions relating to tem- 

 perature, moisture, vegetable growth and decay. But among the 

 vast number of micro-organisms of an infinite variety of species 

 found in localities which are recognized as malarious, the little 

 specks of protoplasm which with a first-class oil- immersion ob- 

 jective, and by careful manipulation of the light we recognize 

 as parasitic invaders of human blood-corpuscles could scarcely be 

 detected, and could not be differentiated from other sjoorelike 



