THE SKELETAL TISSUES. 



ITI 



death. 1 Weyl 2 found the percentage of water in the muscles of 

 torpedo to be 7 7 '5 ; in the electrical organ, 89. He was also able to 

 separate a number of organic substances 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. 



Most 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 conveniently 

 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. 

 Bone earth, 21 '85 ,, 



Zalesky's analyses of dried macerated bone are as follows : 



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 lacunae and canaliculi, 7 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. Anat. u. PhysioL, Leipzig, 1893, S. 99 ; Du Bois-Reymond found 

 that the electrical organ of Malapterurus also becomes acid on activity. 



2 Monatsb. d. Jc. ATcad. d. Wissensch., Berlin, April 1881. 



3 Arch. f. Anat. u, PhysioL, Leipzig, 1884, PhysioL AUh., S. 316. 



4 Lukjanow, Ztsdir. f. physiol. Chem., Strassburg, Bd. xiii. S. 339. 



5 Centralbl.f. d. med. Wissensch., Berlin, 1871, No. 14. 



6 Ann. de chim., Paris, Ser. 3, tome xliii. p. 47. 



7 This substance is not keratin, as Brosicke supposed. See H. E. Smith, Ztschr. f. 

 Biol. , Mlinchen, Bd. xix. S. 469. 



8 R. A. Young, Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 803. 

 9 Rustiksky, Centralbl. f. d. med. Wissensch., Berlin, 1872, S. 562. 



