GLANDULAR ORGANS. 85 
present. 1 The mucus of urine has also been state 1 to be nucleo-proteid in 
nature. 2 K. A. II. Mbrner 3 investigated healthy human urine ; each experiment 
necessitated the use of 80-90 litres. He found proteid or proteid-like materials 
partly in suspension in the ordinary mucous cloud or nubecula, and partly in 
solution. From the nubecula he separated a specific member of the mucin 
group, which he calls urine mucoid. This probably originates from the mucous 
membrane of the urinary passages. It contains C 49 - 4, N 12'74, and 
S -v> per cent. ; and in its general properties agrees with ovo-mucoid pretty 
closely (see p. 63). The soluble proteid in urine, which is present in the 
merest traces, is chiefly serum albumin, but some is precipitable by acetic 
acid, and this part consists of a nucleo-proteid ; precipitated with it was 
found a small quantity of chondroitin sulphuric acid (see " Cartilage " ). 
The mucin of the respiratory passages has been investigated by F. Midler. 4 
He finds it is true mucin, not nucleo-proteid. It yields from 25 to 32 per cent. 
of reducing substance. This is a nitrogenous derivative of a hexose, and is 
probably glucosamine. 
Keratin and the skeletins are epithelial products which have already been 
described (p. 72). The enamel of teeth, although epithelial in origin, will 
be taken with the skeletal tissues. The epithelium of secreting glands will 
be studied with those glands and their secretions. 
Glandular Organs. 
The liver. — The fresh liver is alkaline in reaction, but after death 
soon becomes acid from the development of sarcolactic acid. 
The number of organic substances in the liver is very numerous. 
There are proteids and nuclein from the hepatic cells ; there are 
substances like glycogen, sugar, and fat, stored up within the cells, or 
produced from stored-up substances. Gelatin and mucin are obtainable 
from the connective tissue framework. There are also extractives like 
xanthine, hypoxanthine, and uric acid; lastly, a small proportion of 
inorganic constituents. 
The proportion of water is about 75 per cent. v. Bibra 5 gives the 
following numbers : — 
Water . . 76T7 per cent. Gelatin . . 3 - 37 per cent. 
Insoluble tissues 9 - 44 „ Extractives . 2 -40 „ 
Froteids . .2-40 „ Fats . . 2-50 „ 
Proteids of the liver cells. — These were first investigated by P. Plosz. 
He found that, accompanying the onset of acidity after death, the 
liver became harder and less transparent; he therefore compared the 
condition to the rigor mortis of muscle, and sought for myosin by the 
methods Kiihne had introduced for separating muscle plasma. He did 
not, however, find any myosin. He extracted the proteids by means of 
saline solutions of various strengths, and found — 
(1) A proteid coagulating at 45° C., wholly soluble in gastric digestion : 
(2) a nucleo-proteid, coagulating at 70° C., yielding an insoluble residue of 
1 Hammarsten, Kan. Ges. der TT'iss., Upsala, 1893 {Sejmrat-abzug) ; Baginsky and Somer- 
feld, Verhandl. d. physiol. Gescllsch., Berlin, 1894-5, Kos 13, 14, 15 in Arch. f. Physiol., 
Leipzig, 1895, S. 362.' 
2 Lbiinberg, Upsala Lakaref. Forh., vol. xxv. ; K. Morner, Hygiea, Stockholm, 1892, 
vol. lii ; Obermayer, Centralbl. f. 1:1 in. Med., Bonn, Bd. xii. 
3 Slcandin. Arch. f. Physiol.. Leipzig, 1895, S. 332. 
4 Sitzungsb. d. Gescllsch. z. Befbrd. d. ges. Nainirw. zv Marburg, 1896, No. 6. 
5 v. Bibra, "Chemische Fragmente ueber die Leber," 1849. 
6 Arch. f. d. g<'s. Physiol., Bonn, Bd. vii. S. 371. 
