X XITI.—CasEIn anp 1Ts Primary CLEAVAGE Propucts. By 
R. H. Carrrenpen anp H. M. Parnter, B.A., Pu.B. 
FoLiow1ne out the general plan of procedure indicated some time 
ago with other albuminous bedies,* we have endeavored to prepare 
and study the primary products formed in the digestion of pure casein 
with pepsin-hydrochloric acid. Assuming that casein in its conver- 
sion into peptone by artificial gastric juice, passes through certain 
intermediate stages, in which bodies akin to the albumose bodies 
are formed, we have applied the methods of separation used so suc- 
cessfully in the past and have been able to isolate a class of bodies 
bearing the same relationship to casein that the albumoses do to 
albumin. For this class of bodies we propose the name of caseoses. 
In studying these substances and particularly their composition, 
we deemed it essential to be certain of the purity and composition 
of the casein to be digested; particularly in view of the recent con- 
troversy between Hammarstent and A. Danilewsky as to the single 
nature of this albuminous body. Assuming, as claimed by Dan- 
ilewsky,{ that casein is a mixture of two albuminous bodies and that 
the uumerous analyses recently made by Hammarsten of various 
preparations of casein are incorrect, particularly in the percentage 
of sulphur, made it incumbent on us to obtain some data on these 
points confirmatory of one or the other view, before advancing to a 
study of the products formed by the digestion of casein. 
Of the various methods used for the preparation of pure casein, 
that depending on repeated precipitation by acids and re-solution 
in alkalies has been the most in vogue; for although theoretical 
objections might be advanced as to the possibility of change in the 
nature of the substance under the influence of acids and alkalies, the 
. results obtained have in some respects, at least, been very satisfac- 
tory. Alex. Schmidt, in conjunction with Kapeller,§ showed plainly 
that dialysis of milk and then precipitation of the casein by acetic 
acid, while it gave fairly good results, was not sufficient in itself to 
* See the preceding articles on globuloses and albumoses. 
+ See Zeitschrift fiir physiologische Chemie. Band vii, p. 227. Zur Frage, ob das 
casein ein einheitlicher stoff sei. Also same volume, p. 427. 
+ See Zeitschrift fiir physiologische chemie, Band vii, p. 433. 
§ Beitrag zur Kenntniss der Milch, Jahresbericht fiir Thierchemie, 1874, p. 154. 
