438 RESEARCH IN PROTOZOOLOGY 



will be little variability. The coefficient of variation is ascertained 

 in the following way: 



(i) From each blood smear 50 or 100 parasites are found at 

 random and are drawn by means of a camera lucida at a 

 convenient magnification. 



(2) The total length of each parasite is found. 



(3) The mean ( — I of each sample of 50 or 100 total lengths 



is obtained. (2',r = the sum of the lengths; n = the num- 

 ber drawn.) 



(4) Then the standard deviation! -a^^^^ M^ lis obtained. {Ix"^ 



^ the sum of the squares of the lengths ; n = the number 

 drawn; hP = the square of the mean.) 



(5) Finally, the coefficient of variation f—r-^ lis obtained. (0 ^ 



the standard deviation, M = the mean.) If the coefficient 

 of variation remains constant, the rate of reproduction 

 may be said to remain constant, etc. 



Since the malarial parasites show a synchronicity in their 

 reproductive activity, their rate of reproduction can be obtained 

 directly by ascertaining whether the cycle of growth and sporu- 

 lation takes the same length of time throughout an infection. 

 The methods for ascertaining the cycle of growth and sporula- 

 tion as well a.s its bearing on the rate of reproduction may be 

 found in Chapter XXXVIII by L. G. Taliaferro. 



The work just reviewed leads directly to a consideration of 

 various aspects of the functional role of antibodies, such as the 

 curative and protective action of immune serums, the artificial 

 production of immunity in animals and the cellular basis of 

 antibody production and immunity to protozoa in general. For 

 these phases of the subject, the reader is referred to W. H. Talia- 

 ferro (1929). 



