90 



Drs. B. Blacklock and W. Yorke. 



Prof. Ehrlich informs us that there is no doubt that he obtained it from a 

 trustworthy source. 



Strain C. — East Prussian strain. This strain was supplied to us by the 

 veterinary department of the Kaiserliches Gesundheitsamt. It is the virus 

 responsible for the East Prussian outbreak of Beschalseuche in horses in 

 1905. 



We have made a careful study of the morphology of each of these three 

 strains. For the sake of comparison the infection in rats and guinea-pigs has 

 been observed in each case. On examining the blood of infected guinea-pigs 

 we were at once impressed by the large number of short, aflagellar forms 

 occurring in Strain A as compared with B and C. 



To give mathematical expression to this statement 20,000 individuals of 

 each strain were examined regarding the presence or absence of a free 

 flagellum. The examinations were conducted by observing from 200 to 1000 

 individuals on different days of the infection in both rats and guinea-pigs. 



A glance at Table I will show that the impression — that Strain A is different 

 from Strains B and C — conveyed by casual examination of blood films of 

 guinea-pigs infected with each of these strains is correct, for whereas of the 

 20,000 individuals observed in each strain, 1321 aflagellar and spicule* forms 

 were encountered in Strain A, only 18 and 86 similar forms were seen in 



Table I. — Showing the Number of Parasites of Various Types encountered in 

 20,000 of each of the Three Strains. 



Strain. 



Animal. 



Number 

 observed. 



Forms 

 ■with free 

 flagellum. 



Aflagellar 

 forms. 



Spicule forms or 

 forms with very 

 short flagellum. 



Posterior 

 nuclear 

 forms. 



A 



Guinea-pig ... 

 Eat 



10,000 

 10,000 



8,814 

 9,865 



378 

 30 



80S 

 105 



332 

 128 











Total ... 



20,000 



18,679 



408 



913 



460 



B 



Guinea- pig ... 



Eat 



10,000 

 10,000 



9,986 

 9,996 





 1 



14 



3 





 















Total ... 



20,000 



19,982 



1 



17 







C 



Guinea-pig ... 

 Eat 



10,000 

 10,000 



9,918 

 9,996 



22 







60 

 4 





 













Total ... 



20,000 



19,914 



22 



64 







* By these forms we mean parasites in which the flagellum is free to the extent of 

 about 1 n or less. 



