98 REPORTS ON THE STATE OF SCIENCE.—1918. 
protection of the casein by some agent such as albumen or gelatine is 
most advantageous. 
Alexander, J. Am. Chem. Soc. 32, 680-87 (1910). 
f | Auzol, These de Paris (1907). : 
| OS. gee Health and Mar. Hosp. Serv., Washington, Hyg. Lab. Bull. 41, 
p. 658. 
A most interesting and comprehensive study of “The Coagulation 
of Cows’ Milk in the Human Stomach” has been made by Brenne- 
mann (Arch. Pediatrics 34, 81--117 (1917) ). 
He found that when fresh milk is drunk, the curds formed in the 
stomach are very large and hard, whilst milk boiled for 5 minutes 
gives rise to small soft curds. The curds become harder and bigger 
as the fat content of the milk is decreased. An increased fat content 
leads to smaller and softer curds, but their digestion islessrapid. A 
rapid ingestion of milk produces larger curds than does the sipping 
of milk. 
Diluted milk leads to finer, flakier, and more porouscurds. Lime 
water and milk do not easily coagulate, even if at all. Barley water 
and other starchy decoctions, when added to the milk, lead to 
smaller curds, more easily digested; they exert a ‘‘protective” 
influence over the casein. 
Another phenomenon of great interest in colloid chemistry is 
exhibited when milk is boiled, or made, into milk puddings ete., 
namely, the formation of a skin or membrane at the surface. This 
subject has been investigated by Ramsden :— 
Archi. f. Anat. u. Physiol., pp. 517-534 (1894). 
Proc. Roy. Soc. 2, 156-164 (1903), 
Zeit. phys. Chem. 4'7, 336 (1904). 
Ramsden asserts that for this membrane formation there must be 
present a free (gas) surface, and a general system as follows :— 
water -———— dissolved colloid — — gas. 
Particles of the dissolved colloid passing spontaneously out of 
the solution give rise to a delicate surface pellicle or membrane. 
Ramsden found that all albumins in time can form sucha skin at the 
still surface of their solutions. The colloid lowers the surface 
tension of the liquid and passes into the surface layer (adsorption), 
the process being an irreversible one. Even dilute solutions can 
yield a highly concentrated surface layer, following definite 
mathematical relations ; see Milner (Phil. Mag. 1907 (vi) 18, 96). 
The Fat in Milk Cream. 
Milk contains about 3°6 per cent. of fat, present as an emulsion of 
fair stability. On standing, the greater portion of the fat rises to the 
surface, as cream, and the milk then contains about 0-2 per cent. fat 
(water = 90°4 per cent.). Much argument has taken place as to 
whether the fat globules in milk are surrounded by a membrane, or 
by a gelatinous mucoid substance, semi-liquid, usually referred to © 
under the Danish name ‘“‘slim-membran”. Storch claims to isolate 
this mucoid body by treating cream-until all the lactose, casein, etc., 
has been washed away. Staining milk with ammoniacal picro-— 
carmine, Storch examined the fat globules under the microscope and 
observed a stain layer enveloping each globule. Though he claims 
