74 
Proceedings of Royal Society of Edinburgh. [sess. 
nation of a large number of the granules. All these particles, 
whether in clot or precipitate, stain with osmic acid. 
Further, the so-called “ pure solutions of caseinogen ” or “ sus- 
pensions ” (which seems to be much nearer the truth), whether in 
water or in dilute MgS0 4 , have as many globules and granules as 
whey or diluted milk, e.g ., milk diluted to one in four. Apart 
from these particles they have no caseinogen, and the exhaustion- 
filtrate of “ pure caseinogen ” will not only not clot, but contains 
no proteid or chemical substance at all ; it is water. 
The whey from the acid-precipitate in milk, or the whey from 
the rennet clot, are alike turbid, owing to the large number of both 
globules and granules which they contain ; accordingly, I find I can 
obtain from either of them a precipitate with acetic acid, and a 
clot with rennet, calcic phosphate, and phosphoric acid present 
together, of course very open as solidifications, yet, microscopically, 
indistinguishable from the original clots in milk, and with all their 
particles stainable by osmic acid. 
Further, as scrutinised under the microscope, the actions of acid 
and rennet on a hot-stage are identical, resulting in an agglutina- 
tion of multitudes of granules and some globules, many of both 
kinds remaining isolated in the whey. 
Halliburton* states that Hoppe-Seyler got as much “ casein from 
cream, as from portions of milk below the cream” — presumably 
from equal weights of cream and milk below it. In other words, 
there is as much caseinogen associated with the large oil-globules 
(the cream ) as there is with the smaller globules and smallest 
particles in the skimmed milk below. 
Cream is but the comparatively quickly-formed aggregation of 
the larger oil-globules risen to the surface, these being so much 
lighter than their bulk of plasma ; a centrifuge hastens this separa- 
tion, but never effects a complete separation of the “ cream ” or 
“ fat,” for the same reason that after a certain time some particles 
will never rise to the surface of skimmed milk, it can be no more 
“ creamed ” ; but is still opalescent, and contains fat on analysis. 
How, if these smallest particles were fat alone, they ought in 
time to rise to the surface of skimmed milk, and ought always to 
be separated by the “ centrifuge ” * the only inference is, not that 
* Chemical Physiology, p. 57 5. 
