THE SKELETAL TISSUES. iti 
death. 1 Weyl 2 found the percentage of water in the muscles of 
torpedo to be 77 - ~> : in the electrical organ, 89. Ee was also able to 
separate a number of organic Bubstances from the organ, similar to 
those occurring in muscle and nerve, such as creatine, xanthine, 
lecithin, fat, cholesterin, fatty acids, and inosite. Frerichs and 
Stadeler found urea. In another research, Weyl 3 found that excitation 
of the organ produced an increased formation of phosphoric acid in it. 
The Skeletal Tissues. 
Mosl of the chemical substances occurring in the connective tissues 
(collagen, elastin, mucin, fat ) have been already described (see pp. 69-72). 
There are still a few to be discussed, which will be most cimveniently 
done under the heads — Bone, Tooth, Cartilage, and Notochord. 
Bone. — -Bone differs from most other tissues in its high percentage of 
mineral matter. It contains 46 '7 per cent, of water, 4 of which Aeby 5 
considers 11 or 12 are in a state of loose chemical combination, 
analogous to water of crystallisation. 
The composition of undried bone without separation of marrow or 
blood is given by Hoppe-Seyler thus : — 
"Water, 50 00 per cent. 
Fat, 15-75 „ 
Ossein, 11-40 per cent. 
Eone earth, 21*85 ,, 
Zalesky's analyses of dried macerated bone are as follows : — 
Human Eone. 
Bone of Ox. j Bone of Guinea-Pig. 
Organic constituents . 
Inorganic ,, 
34-56 
65-44 
32-02 
67-98 
34-70 
65 -30 
Fossil bones analysed by Fremy 6 show a smaller percentage of 
organic matter. 
The organic constituents of bone are ossein or collagen, small quantities 
of elastin from the lining of the lacunas and canaliculi," proteids, and 
nuclein from the cells, and a small quantity of fat even after the removal 
of all the marrow. The absence of mucin in compact bone is noteworthy, 
showing that the ground substance is entirely replaced by calcareous 
matter. 8 Marrow, however, yields mucin. 9 The inorganic constituents 
of bone are calcium phosphate, calcium carbonate, calcium chloride, 
calcium fluoride, magnesium phosphate, and small quantities of sulphates 
and other chlorides. 
1 Boll, Arch. f. Aitat. u. Physiol., Leipzig, 1893, S. 99 ; Du Bois-Reymond found 
that the electrical organ of Malapterurvs also becomes acid on activity. 
- Monatsb. d. k. Akad. d. Wissensch., Berlin, April 1881. 
3 Arch. f. Anat. u. Physiol., Leipzig, 1884, Physiol. AUh., S. 316. 
4 Lukjauow, Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 339. 
5 C'entralbl. f. d. vied. Wissensch., Berlin, 1871, No. 14. 
6 Ann. de chim., Paris, S£r. 3, tome xliii. p. 47. 
7 This substance is not keratin, as Brosicke supposed. See H. E. Smith, Ztschr. f. 
Biol. , Mtinchen, Bd. xix. S. 469. 
8 R. A. Young, Journ. Physiol., Cambridge and London, 1892, vol. xiii. p. 803. 
9 Rustiksky, Centra I ol. f. d. med. Wissensch., Berlin, 1872, S. 562. 
