290 



THE PROTOZOA 



parasites are much more resistant. Bass thinks he observed parthenogen 

 The temperature should be from 40 to 4iC. and strict anaerobic conditions ob- 

 served. ^Estivo-autumnal organisms are more resistant than benign tertian ones. 

 Dextrose seems to be an essential for the development of the parasites. 



Bass considers that P. vivax has a disc-like structure which enables it to squeeze 

 through the brain capillaries while adult schizonts of P. falciparum have a solid 

 oval form which causes them to be caught in the capillaries. 



The Thompsons have rather .simplified the method of Bass. They draw 10 c.c. 

 of blood into a test-tube containing the usual amount of glucose solution. They 

 then defibrinate the blood by stirring with a thick wire for about five minutes and 

 remove the wire with the adhering clot. They then pour this defibrinated blood 

 into several small sterile test-tubes, which should contain at least a i-inch column. 

 Rubber caps are adjusted over the cotton plugs and the tubes placed in the incu- 

 bator. They note the tendency of cultures of P. falciparum to agglutinate which 

 is not true of P. vivax. 



They think this agglutination the great cause of the plugging of capillaries in 

 pernicious malaria. They note 32 merozoites as maximum number in sporulation 

 of P. falciparum while P. vivax has usually 16 or more, but never as many as 32 



This would explain the shorter incubation period of malignant tertian. The 

 pigment of P. falciparum clumps much earlier in. the developing schizont than that 

 of P. vivax and is much coarser and more discrete. 



While Bass thought he noted parthenogenesis in cultures others have failed to 

 observe any evidence of it. 





UNSTAINED SPECIMEN (FRESH BLOOD) 



