140 



AGE, GROWTH, AND DEATH 



parasite's development is distributed as a series of 

 small scattered granules, which cannot be demon- 

 strated satisfactorily until they have been artificially 

 coloured. The parasite itself is a small mass of un- 

 differentiated protoplasm. In another stage of its life 

 cycle the Plasmodium vivax has a distinct nucleus 

 with only a very little protoplasm, and while in that 

 stage it multiplies with that enormous rapidity which 

 renders it such a dangerous parasite to the human 

 race. I will now show you another picture of parasites 



FlG. 50. Trypanosoma Lewi.n, from the rat's 

 blood, with two blood corpuscles alongside drawn 

 on the same scale, by E. S. Kilgore. 



one form of which, in a related species, occurs in 

 man. This particular form is one which occurs in the 

 rat and is called the Trypanosoma. You can see that 

 the body, instead of being a small and simple struc- 

 ture, has elongated, acquired a peculiar form, and 



