50 CHEMICAL CONSTITUENTS OE BODY AND FOOD. 
ammonium sulphate. Their solutions are coagulated by heat, the 
temperature of heat coagulation varying considerably. Fibrinogen, 
serum globulin, globin, paramyosinogen, and myosinogen, crystallin, 
vitellin, 1 egg globulin are examples. 
The differences in solubility of these two important classes of native 
proteids may be stated in tabular form as follows : — 
Reagent. Albumin. 
Globulin. 
Dilute saline solution ..... ,, 
Saturated solution of magnesium sulphate or 
sodium chloride ...... ,, 
Half-saturated solution of ammonium sulphate ,, 
Saturated solution of ammonium sulphate . Insoluble 
i 
Insoluble 
Soluble 
Insoluble 
Class 3. Albuminates. — These arc proteids derived from either 
albumins or globulins by the adiou of weak acids or alkalis. The term 
has been extended to include metallic compounds of the proteids, hut 
restricting it here to acid albumin or syntonin, ami alkali albumin, the 
class may be defined as consisting of proteids which are insoluble in 
water, and in neutral solutions containing no salt. They are soluble in 
acid or alkaline solutions, and in weak saline solutions. They are 
precipitated by neutralisation, and resemble globulins in their behaviour 
to neutral salts. Their solutions are not coagulated by heat. 
A less soluble variety of these proteids, called Lieberkiilm's jelly, 
is formed by adding strong acid or alkali respectively to undiluted 
white of egg. 
Caseinogen, formerly regarded as a member of this group, will be 
studied with nucleo-proteids and with milk. 
After egg albumin is treated with formaldehyde it remains soluble 
in water, but is not coagulable on heating. 2 
Class 4. Products of proteolysis ; proteoses and peptones. — These will 
be studied in detail in connection with digestion. They can, however, 
lie formed by other hydrolysing agencies than digestive juices, such as 
l re anient with mineral acids, or superheated steam. 3 The term proteose 
for the intermediate products of hydration is a convenient general name, 
which includes not only albumoses, but also vitelloses, globuloses, caseoses, 
myosinoses, and the like. 
Class 5. Coagulated proteids. — This class includes the proteids in 
which coagulation has been produced by heat, and those in which coagu- 
lation has been induced by ferment action, such as fibrin, myosin, casein, 
and anti-albumid, an insoluble by-product formed in gastric digestion. 
Since the individual members of these groups have either been 
described in preceding sections, or will be discussed elsewhere under 
other heads, such as blood, milk, etc., they need not be further considered 
in this place. 
1 Vitellin, unlike other globulins, is not precipitated by sodium chloride. Some regard 
it as a nucleo-prote'id. It will be more fully discussed later. 
-Blum, Ztschr, f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 127; Berl. klin. 
Wchnschr., 1897, Bd. xxxiii. S. 1013. 
3 On " Atmid -albumoses " (that is, those formed by superheated steam) see Neumeister, 
Ztschr. f. Biol., Munchen, Bd. xxvi. S. 57 ; Chitteudeu arid Meara, Journ. Physiol., 
Cambridge and London, 1894, vol. xv. p. 501. 
