THE PR O TEWS OF MILK. 1 3 7 
the pseudo-nuclein is partly soluble in gastric juice; 1 it is by far the 
most Boluble of the uucleins, 2 though the majority are partly soluble 
after pancreatic digestion. 3 
Casern. — This name should be restricted to the proteid formed by 
the action of rennin, or of ferments thai act like rennin. As a general 
rule, it is more insoluble than caseinogen : it is, however, readily soluble 
in dilute alkalis such as lime water. From these solutions it is readily 
precipitable by traces of calcium chloride; and also by sodium chloride 
(Hammarsten). The precipitate with calcium chloride increases on 
heating, but, like many calcium compounds, partially redissolves on 
cooling (Binger). 
The main distinction between casein and caseinogen is, however, 
that which was first insisted on by Hammarsten, namely, that caseinogen 
can be curdled by rennet, casein cannot. Some recent work by I). F. 
Harris i and Peters 5 appeared to cast doubt upon this essential distinction, 
and to suggest the possibility of recoagulation of casein, analogous to 
that of myosin. The fallacies into which these observers were drawn 
have been pointed out independently by Edmunds, 6 Hammarsten, 7 and 
E. Benjamin. 8 Peters, for instance, used a preparation of rennet, rich in 
soi lium chloride and calcium salts ; the precipitate he obtained by adding 
this to a solution of casein was due to these salts, not to the ferment. 
Pancreatic casein. — An interesting variety of casein is that formed 
by the action of pancreatic juice on milk, which has been recently 
investigated by Brodie and myself. 9 
Kiihne 10 was the first to point out that extracts made from the 
pancreas of the dog cause milk to coagulate ; this action was described 
in some detail by Sir William Roberts. 11 Various conditions which 
influence the clotting were observed by Edkins, 12 and the occurrence of 
the action in pancreatic extracts from a number of animals determined by 
Harris and Grow. 13 
Our attention was drawn to the subject by a sentence in Prof. 
Gamgee's " Physiological Chemistry," 14 in which he points out that it does 
not necessarily follow that because extracts of the organ have a clotting 
action, the pancreatic juice possesses it also. 
We accordingly performed experiments with the actual pancreatic 
secretion, obtained from temporary fistuke in dogs, and our conclusions 
are summarised as follows : — 
1. The pancreatic juice obtained from temporary pancreatic fistuke, 
from dogs, produces a change in the caseinogen of milk. 
1 The nutritive value of casein is given by Marcuse (Arch. f. d. gcs. Physiol., Bonn, Brl. 
lxii. S. 223) as equal to that of meat proteids. 
2 E. Salkowski ( Virchovfs Archie, Bd. cxliv.) states that caseinogen, if not coagulated in 
the process of preparation, is completely digested by gastric juice, if a sufficient volume of 
the latter is employed, e.g. 500 parts of gastric juice to 1 of caseinogen. 
3 Sebelien, Ztschr. f. physiol. Chem., Strassburg, Bd. xx. ; Popoff, ibid., Bd. xviii. ; 
Gumlich, ibid., Bd. xviii. ; Weintrand, Verhandl. J. physiol. Gesellsch., Arch. f. physiol., 
Berlin, 1895; Clara Willdenow, Inaug. Diss., Bern, 1893 ; W. Sandmeyer, Ztschr. f. 
physiol. Chem., Strassburg, 1895, Bd. xxi. S. 87. 4 Loc. cit. 
5 Preisschrift, Rostock, 1894. 6 Loc. cit. 
7 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 103. 
8 Vircliow's Archiv, 1896, Bd. cxlv. S. 30. 
9 Journ. Physiol., Cambridge and London, 1896, vol. xx. S. 97. 
10 Verhandl. d. naturh.-med. Vcr. zu Heidelberg, IS. ¥., Bd. iii. S. 3. ■ 
11 Proc. Roy. Hoc. London, 1879 and 1881. 
12 Journ. Physiol., Cambridge and London, 1S91, vol. xii. p. 193. 
13 Ibid., 1892, vol. xiii. p. 469. 14 Vol. ii. p. 446. 
