152 H. S. H. WARDLAW. 
On THE NATURE oF THE DEPOSIT OBTAINED FROM MILK 
BY SPINNING In A CENTRIFUGE. 
(Preliminary Communication. ) 
By H. 8. HALCRO WARDLAW, B.Sc., 
Science Research Scholar of the University of Sydney. 
(From the Physiological Laboratory of the University of Sydney.) 
[Read before the Royal Society of N. 8. Wales, July 1, 1914.} 
_ WHEN milk is kept in a sterile condition for long periods 
of time (several years), a white deposit is observed to 
collect on the bottom of the containing vessel. Salkowski 
(1900) regards the deposit so obtained as precipitated 
caseinogen, while Langlois (1913) considers it to be tri- 
calcium phosphate. Preti (1907) has determined the ash, 
calcium, and phosphorus of the deposit obtained in this 
way, and found 32°11% ash, 10°7% calcium, 4°33 phosphorus, 
and on the basis of these results regards the deposit as a 
mixture of tricalcium phosphate and a calcium compound 
of caseinogen. Neither Salkowski nor Preti came to a 
conclusion as to whether the appearance of this deposit 
was due to purely physical phenomena, whether it was due 
simply to the action of gravity on suspended matter in 
milk, or whether it was due to traces of rennin, or to the 
occurrence of slow chemical changes. 
When milk is spun ina centrifuge, Barthel(1910) observed 
that a deposit similar to the above is obtained in the 
centrifuge tubes; he considers the deposit to be a mixture 
of calcium phosphate and casinogen. Im this case, as the 
time required to obtain the deposit is quite short, the action 
of traces of rennin or of slow chemical changes is practi- 
