From 
From 
Hoppe-Seyler. 2 
Dreehsel. 3 
5] ■') to 54 - 5 
50-0 to 55-0 
6-9 „ 7-3 
6-8 „ 7-3 
15-2 „ 17-0 
15-4 „ 18-2 
20-9 „ 23-5 
22-8 „ 24-1 
0-3 „ 2-0 
0-4 „ 5-0 
COMPOSITION OF THE P ROTE IDS. 25 
Tlic proteid constituents of the animal body are derived from 
vegetables either directly, or indirectly through the body of another 
animal. Synthetic processes do occur in the animal body, 1 hut to a 
much greater extent in vegetables; here the proteids are buill up from 
simpler compounds, derived ultimately from the soil and atmosphere. 
In animals, the proteids are converted during digestion into hydrated 
products, called peptones; these are re-converted into proteids, 
similar, in a general sense, to those originally ingested, and these are 
assimilated to become part of the living organism. In time, they 
become subjected to katabolic processes, and give rise to carbonic acid, 
sulphuric acid, water, and certain not fully oxidised products (urea, uric 
acid, etc.) which contain the nitrogen of the original proteid. 
Composition of the proteids. — Various proteids differ a good deal 
in elementary composition, as is seen by the following percentages : — • 
C 
II 
N 
(J 
S 
In addition to the above constituents, many proteids or proteid-like 
substances contain small quantities of phosphorus ; and practically all 
proteids leave on ignition a variable amount of ash. In the case of egg- 
albumin the chief substances in the ash are chlorides of potassium and 
sodium, and smaller quantities of phosphoric, sulphuric, and carbonic 
acids, in combination with sodium, potassium, calcium, magnesium, and 
iron. There may also be a trace of silica. 4 The ash of serum pro- 
teids contains an excess of sodium chloride, and that of muscle proteids 
a preponderance of potassium and phosphoric acid. 
Whether these mineral substances are integral constituents of the proteid 
molecule, or closely adherent impurities, is a matter of doubt ; the latter 
supposition is the more probable, as there are certain methods of obtaining 
proteids practically free from ash. The best of these is Ilarnaek's, ' in which 
he precipitates the proteid as a copper albuminate; this is dissolved in sodium 
hydrate, and the proteid is precipitated from this solution by hydrochloric acid. 
The so-called ash-free albumin obtained earlier by Aronstein and Schmidt 1 ' by 
means of dialysis, was shown by later observers (Heynsius, Winogradoff) to he 
poor in ash, but not free from ash, and, moreover, that its incoagulability by 
heat and other characteristic properties were due to the use of alkali in its 
preparation. Nevertheless, Harnack's ash-free albumin is also not coagulable 
by heat, and more closely resembles acid albumin in its properties than any 
other known proteid." 
1 A very suggestive article by Pfliiger on this subject will be found in Arch. f. d. ges. 
Physiol., Bonn, Bd. xlii. S. 144. 
- " Handbuch d. physiol. path. cbem. Anal.," 18S5, 5th edition, S. 258. 
3 Loc. cit. Kiihne and Chittenden's analyses of peptones, which they give with reserve, 
lie considerably outside these limits, Ztsehr.f. Biol., Miinchen, 1886, Bd. xxii. S. 452. 
4 Gmelin, "Handb. d. org. Chem.," Bd. viii. S. 285. 
5 Ber. d. deutsch. rj,em. Gesellseh., Berlin. Bd. xxii. S. 3046; Bd. xxiii. S. 374.". ; Bd. xxv. 
S. 204. 
6 Arch. f. d. ges. Physiol., Bonn, 1875, S. 1. 
7 Werigo, ibid., Bd. xlviii. S. 127. Harnack denies that his material is acid -albumin, 
in si.ite of the acid used in its precipitation. 
