Variations in Resistance of Red Blood Cells. 163 



laking by amboceptor and complement or was a general resistance 

 such as would be shown by an increased resistance to laking by 

 hypotonic salt solution, and also whether the sera of different 

 sheep show similar differences in their tonicity. 

 Three sheep were used : — 



T — an apparently normal young male sheep, newly obtained 

 from the dealer. 



F — a sheep which had been kept in the laboratory for six months 

 and had been bled repeatedly and on occasions profusely. 



P — a sheep which had been confined for two and one half years, 

 had been bled occasionally and had received immunizing injections 

 of typhoid bacilli for a period of about eighteen months. 



F was slightly and P decidedly anemic. The blood of all 

 three was obtained on the same day and the cells were washed with 

 great care to handle the blood of all three animals in precisely 

 similar ways. All three were made up into 5 per cent suspension 

 and tested with diminishing quantities of hemolytic amboceptor 

 (rabbit serum) and a fixed dose of 10 per cent complement (guinea 

 pig) with the following result : 



table I. 



Variations in Resistance to Lytic Serum. 



Each tube contains 0.5 c.c. 5 per cent, washed red cells, 0.1 c.c. of 10 per cent, 

 guinea-pig complement and the amount of immune serum indicated below. Incuba- 

 tion one-half hour. 



(1/600) Amboceptor. 



.1 



.15 



.2 



2-5 



3.0 



Cells of sheep P 



+ + + 



+ + + + 



+ + + + 



+ + + + 



+ + + + 



Cells of sheep F 



+ + 



+ + + 



+ + + + 



++ + + 



+ +++ 



Cells of sheep T 



+ 



+ + 



+ + + + 



++++ 



+ + + + 



( + + + + = complete hemolysis.) 



It is seen that the new sheep, T, was the most resistant to 

 laking, the frequently bled sheep, F, almost as resistant, and the 

 typhoid injected sheep, P, least resistant. 



At the same time the washed cells were tested for their sus- 

 ceptibility to laking by anisotonic salt solutions, by adding .2 c.c. 

 of 30 per cent suspension of cells of each sheep to 5 c.c. of salt 

 solution whose strength ranged from .3 per cent to 9 per cent with 

 intervals of .025 per cent. 



The new sheep (T) was then bled 800 c.c. and the blood of all 



