228 PATHOGENIC MICROORGANISMS. 



water three or four times, then dried and mounted in balsam, 

 and examined. In this preparation the red cells will be stained 

 pinky the leucocytes pale blue and their nuclei dark blue; the 

 parasites will be stained very dark blue and their pigment- 

 granules remain unstained. 



The mixture of methylene-blue and eosin is prepared as 

 follows : 



Saturated aqueous solution of methylene-blue, 1 part ; 

 Alcoholic solution of eosin (1 per cent.), 2 parts. 



Do not filter. 



Giemsa's, Leishman's, and Wright's are best routine stains. 



Loeffler's methylene-blue, and Ehrlich's hsematoxylin and 

 eosin, give also at times very excellent preparations. 



The varieties of plasmodia may be distinguished from each 

 other. 



Differentiation between the Tertian and Quartan Parasites : 



1st. The tertian parasite completes its life-cycle in two 

 days ; that of the quartan requires three days. 



2d. The tertian parasite has a tendency to discolor the 

 blood-cells and to enlarge them. The quartan does not dis- 

 color so much, and never enlarges its containing red cell ; on 

 the contrary, the cell generally appears smaller. 



3d. The quartan parasite has better-defined and clearer 

 outlines and coarser pigment-granules than the tertian. 



4th. In fission the quartan parasite divides into six to 

 twelve daughter cells, which are larger and contain each a 

 refractive granule in its centre. The tertian parasite divides 

 into fifteen to twenty daughter cells, smaller, and with no 

 central granule. 



Inoculation. Blood infected with either kind of parasite 

 when inoculated into healthy individuals has in a number of 

 cases produced that variety of fever specific for the particu- 

 lar parasite, and this special parasite has been found in the 

 blood of the inoculated individual. 



