1908.] Diphtheria Antitowin. 403 
Percentage of Percentage of protein 
alcohol. precipitated. 
12°5 3°6 
25°0 76 
37°5 48°7 
50°0 97 
75°0 99 
The greater bulk of the protein is seen to be precipitated between 25 and 
50 per cent.*alcohol. 
Antitoxin tests were made on the filtrate after precipitating with definite 
percentages of alcohol. It may be stated that alcohol in the dilutions used 
does not destroy toxin. From the antitoxin tests it was found that no 
antitoxin was precipitated by 25 per cent. alcohol; 25 per cent. was pre- 
cipitated by 37:5 per cent. alcohol; 30 per cent. by 40 per cent. alcohol; and 
66 per cent. by 44 per cent. alcohol. From these figures it is legitimate to 
assume that antitoxin has the same precipitation limits as the general mass 
of protein of the particular serum used. 
From the antitoxin tests on the alcohol precipitation of other sera it 
appeared that the greater part of the antitoxin was precipitated between 
35 and 45 per cent. alcohol. 
A point of some importance was to see whether the presence of antitoxin 
in serum had any general influence on the form of the alcohol precipitation 
curve. The quantitative precipitations of four sera of different antitoxin 
values were therefore determined. 
Antitoxin value 
Serum. per c.c. Total solids in 100 c.c. 
Be Melee ieee, 150 9°6 grammes 
| oie Meenas 250 11:0 ‘5 
Or oe de 600 G29 jules 
h Aen SCARRED eric 800 9°7 3 
Weight of protein precipitated from 109 c.c. of serum. 
Percentage of 
alcohol. | 
A B. C D 
grammes. grammes. grammes. grammes. 
30 le 1‘1 — — 
33 2°53 2°0 2:0 2°0 
36 2 86 3 °4 3:1 3°3 
39 3°8 4°6 41 4°7 
42 4°83 6°0 5 °2 5°7 
45 6°7 8°3 6:3 6:9 
48 7-96 9 ‘92 es 8:0 
50 8°52 — Vet d 8 °3 
VOL. LXXX.—B. Zt 
