24 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 
It forms, like glycerine, compounds often called esters, with fatty acids ; 
and these compounds, which are found in the fatty secretions of the skin, 
especially in the fat of sheep's wool (lanoline), are very resistant to bacterial 
action ; as a protection to the skin lanoline is therefore admirable. 
In lanoline there are two cholesterins at least ; one is levorotatory, the 
other (isocholesterin) is dextrorotatory. Isocholesterin was first described 
by Schultze, 1 and does not give Salkowski's reaction. 
Cholesterins of various kinds are present in vegetable tissues. - 
The cholesterin of the blood is in combination with oleic and palmitic 
acids. 3 
In man the cholesterin of the bile passes away in the faeces as koprosterin 
(Co 7 H 4S 0) ; in the horse as hippokoprosterin (Co 7 H 54 or Co 7 H 50 O) ; in the dog 
it is unchanged. 4 
The Proteids. 5 
The proteids are the most important substances present in animal 
and vegetable organisms; none of the phenomena of life occur without 
their presence : they are constant decomposition products of, and therefore 
probable constituents of, protoplasm. 
"They are highly complex and, for the most part, unerystxallisable 
compounds of carbon, hydrogen, oxygen, nitrogen, ami sulphur, 6 occurring 
in a solid, viscous condition, or in solution in nearly all the solids and 
liquids of the organism. The different members of the group present 
differences in physical, and to a certain extent even in chemical 
properties. They all possess, however, certain common chemical reactions, 
and are united by a close genetic relationship " (Gamgee). 7 
The following table from Gorup-Besanez 8 exhibits the percentage of 
proteids contained in the liquids and solids of the body : — 
Cerebrospinal fluid . 0-09 Chyle 4-09 
Aqueous humour . . - 14 Blood . . 8'56 
Liquor amnii . . O70 Spinal conl . . 7 "49 
Intestinal juice . . 095 Brain . . . S - 63 
Pericardial fluid . . 2-36 Liver . . . 1LG4 
Lymph . . . 2-40 Thymus . . 12-29 
Pancreatic juice . . 3 - 33 Muscle . . 16T8 
Synovia . . . 3 - 91 Tunica media of arteries 27"33 
Milk . . . . 3-94 Crystalline lens . 38-30 
1 Ber. d. deutsch. chem. GeseUsch., Berlin, Bd. vi. ; Journ. f. prakt. CJirm., Leijizig, 
X.F., Bd. xxv. S. 458; Ztsehr. f. physiol. Chem., Strassburg, Bd. xiv. S. 522. On 
isocholesterin in vemix caseosa see Rappel, ibid., Bd. xxi. 8. 122. 
2 Beneke, Jahresb. ft. d. L&istwng d. ges. Med., Berlin, 1S62 ; Hesse, Ann. J. 
Chem., Leipzig, Bd. excii. S. 177 ; Bd. ecx., S. 283 ; Reinke and Rodewald, ibid., Bd. 
ccvii. S. 232; Schulze and Barliieri, Journ. f. prakt. Chem., Leipzig, N.F., Bd. xxv. S. 
159, 458; Heekel and Schlagdenhauffen, Compt. rend. Acad. d. sc, Paris, 1886, tome cii. 
p. 1317 ; Arnaud, ibid., p. 1319. See also Jacobson's paper on ' ; Vegetable Oils," Ztsehr. 
/.physiol. Chem., Strassburg, Bd. xiii. S. 32. 
3 K. Hurtble, Ztsehr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 331. 
4 St. Bondzynski and V. Hunmicki, Ztsehr. f. physiol. Chem., Strassburg, 1896, Bd. 
xxii. S. 396. 
5 In the preparation of this section I have derived special assistance from the articles 
"Eiweisskbrper," in Beilstein's " Handbuch der org. Chemie," and in Ladenburg's 
" Handwiirterbui'h d. Chemie," 1885, Bd. iii. S. 534 (article by E. Drechsel) ; and from 
an article by T. G. Brodie in Science Progress, London, 1895, vol. iv. p. 62. 
In some cases phosphorus also is present. 
7 "Physiological Chemistrv," London, vol. i. p. 4. 
8 "LehrbuchV'S. 128. 
