204 TWENTY-FIFTH ANNIVERSARY REPORT. 
casein and calcium oxide, containing about 1.50 per ct. of calcium 
oxide, known as neutral calcium casein. These facts were first made 
known by Soldner and were confirmed by our work, in which these 
products were isolated and studied more thoroughly. Similar prepa- 
rations were made with paracasein. 
(4) Comparison of properties of casem and paracasein, and 
their calcium compounds.— Basic calcium casein and paracasein ap- 
pear soluble in water, forming slightly opalescent solutions. Neither 
is coagulated by rennet, but both are precipitated by soluble cal- 
cium salts on warming. Neutral calcium casein is coagulated by 
soluble calcium salts in warming to 35° to 40° C., but not at 
ordinary room temperature, while neutral calcium paracasein is com- 
pletely and quickly coagulated at room temperatures by soluble 
calcium salts. Neutral calcium casein behaves like milk-casein in 
its behavior toward soluble lime salts on warming, and at ordinary 
temperatures after treatment with rennet, and casein is probably 
present in cows’ milk as the neutral calcium casein. 
Freshly prepared casein and paracasein, when apparently base- 
free and in the presence of soluble calcium salts, are readily soluble 
in warm 5 per ct. salt solution and in hot 50 per ct. alcohol. When 
freshly prepared and sufficiently warmed, they become very plastic 
and ductile, capable of being drawn out in fine, long, silky threads. 
Whether the presence of soluble calcium salts is, as claimed by 
Laxa, in any way responsible for these properties can not be stated 
at present, but in all the experiments made soluble calcium salts 
were present, 
(5) Suggestions regarding nomenclature of casein and para- 
casein and their compounds.— In most of the literature on the sub- 
ject, the word casein is used indiscriminately to mean milk-casein, 
free casein, or those casein salts formed by acid precipitation. In 
many cases it is used comprehensively to include all the proteids 
in cows’ milk. A similar state of confusion exists in regard to 
the use of the word paracasein. It would therefore seem pertinent 
‘to make the following suggestions, tentatively at least, in regard 
to the nomenclature of these compounds. 
(1) That the word casein be applied only to the free protcid, 
that is, the base-free casei. 
(2) That the compound existing n cows’ milk and commonly 
called casein be called calcium casein. 
(3) That the casein compound containing about 2.40 per ct. of 
CaO be called basic calcium casein. 
