72 
Proceedings of Royal Society of Edinburgh. [sess. 
Some Points in the Physiological Chemistry and Co- 
agulation of Milk. By David Fraser Harris, B.Sc. 
(Bond.), M.B.C.M., F.R.S.E. Communicated by John G. 
M ‘Kendrick, M.D., Professor of Physiology in the University 
of Glasgow.* 
(Read March 2, 1896.) 
I. The Physico-Chemical Condition of Caseinogen in Milk. 
According to the latest views of physiological chemists, the 
innumerable fine particles of milk are identified with the caseinogen. 
For instance, Halliburton! regards these particles as caseinogen 
and nuclein which are obviously not fat-globules; and Stirling! 
unhesitatingly accepts the view of the particulate nature of this 
proteid, adducing as proof the fact of the absence of all particles 
from the filtrate of milk through a porous clay-filter. 
I used a “Berkefeld” diatomaceous filter (holding 150 c.c.) said 
to “ sterilise ” water. On immersing it in milk, and by creating a 
partial vacuum inside it, there was obtained an exhaustion-filtrate 
perfectly limpid and free from all particles. Unless sterilised by 
heat, a vigorous growth of fungi appeared in it, there being 
abundant nourishment for them, seeing that it contains lactose, 
chlorides, phosphates, sulphates, calcium, and a proteid (undoubtedly 
the lact-albumin), but is incapable of clotting with rennet. Its 
reaction is faintly acid. Caseinogen cannot, then, be held to be 
“ dissolved ” in the plasma, in the ordinary sense of a “ solution,” 
else this pressure-filtrate would be coagulable ; and only as a last 
resource should we fall back upon the rather unsatisfactory hypo- 
thesis that it may be present as molecules too large to pass through 
the pores of a diatomaceous filter. 
There is in milk undoubtedly, besides what we have been accus- 
tomed to call the oil-globules, a very large number of extremely 
minute particles or granules exhibiting Brownian movement, and 
* From the Physiological Laboratory of the University of Glasgow. 
t In his Chemical Physiology and Pathology, 1891, p. 574. 
X In his Outlines of Practical Physiology, 1895, p. 96. 
