250 Some New Constituents of Milk. III 
These experiments show that Fraction III sensitized guinea 
pigs to the alcohol-soluble protein obtained from the aleoholic 
washings of casein, but not to Fraction I. That no anaphylaxis 
reaction was obtained between Fractions I and III would at first 
sight seem strange, for while the methods employed for separating 
these fractions might lead to a fairly complete separation of the 
alcohol-soluble protein from Fraction I a complete separation of 
the latter from Fraction III could hardly be expected. The failure 
of Fractions I and III to react with one another, however, can 
be explained by the fact that numerous anaphylaxis experiments 
with many different preparations of the proteose-like products 
which we have obtained from milk showed that these were mostly 
destitute of anaphylactogenic power. The slight reactions 
which were occasionally obtained can now be easily explained by 
the presence of the alcohol-soluble protein in some of the prepa- 
rations used. 
Properties of the Alcohol-Soluble Milk Protein. 
The preparations of the alcohol-soluble milk protein are un- 
questionably acid compounds, for when 1 gm. is suspended in 
50 ce. of water 2.5 ce. of 0.1 Nn NaOH solution’ are required to 
obtain a neutral reaction to phenolphthalein. A slightly turbid 
solution is thus formed which becomes distinctly more turbid when 
0.5 ec. of 0.1 n HClis added. On continuing the addition of acid 
up to 1.3 cc. a coarse flocculent precipitate separates leaving the 
solution practically clear. At this reaction very little remains 
dissolved. 
Conversely when 1 gm. is suspended in 50 ec. of water a tur- 
bid solution results in which a not inconsiderable quantity re- 
mains undissolved.’ When0.1 n NaOH solution is gradually added 
the protein separates in coarse flocks, nearly all being precipitated 
when 1.2 cc. has been added; 7.e., at the same reaction as that 
at which it separates on adding acid to the solution neutralized 
to phenolphthalein. When an equal volume of absolute alcohol 
is added most of the suspended protein dissolves after vigorous 
stirring. On standing, the slightly turbid solution deposits a 
transparent varnish-like layer which is readily soluble in warm 
70 per cent alcohol, but from which a part separates on cooling 
