44 SPECIAL HISTOLOGY. 



Molar of a 

 Woman of 25. 

 Phosphate of lime, with some fluoride of 



calcium 67'54 



Carbonate of lime 7*97 



Phosphate of magnesia .... 2-49 



Salts 1-00 



Cartilage 20-42 



Fat 0-58 



10000 



Organic substance . . . .21-00 



Inorganic substance .... 79*00 



In fresh teeth, Pepys found 28 p. c. cartilage, 62 inorganic 

 matter, 10 water and loss; and according to Tomes, teeth, after 

 the pulp is removed, lose in drying J — i of their weight. The 

 organic basis of the teeth, which may readily be obtained by 

 treating them with hydrochloric acid, is identical in all respects 

 with that of the bones and is readily changed into gelatin by 

 boiling. This so-called cartilage of the tooth retains the exact 

 form of the dentine and its external structure also; the 

 tubules, however, are seen with difficulty. If it be macerated 

 in acids or alkalies until quite soft, the matrix undergoes in- 

 cipient solution, but the dentinal tubules, with their walls, offer 

 greater resistance, and may be readily and abundantly isolated, 

 (see ' Mikr. Anat.' ii, 2, p. 61, fig. 189). By still longer 

 maceration, all is dissolved. If teeth be heated to redness, 

 or treated with caustic alkalies, the inorganic portions likewise 

 retain the form of the tooth. It follows, then, that the same 

 intimate mixture of inorganic and organic parts occurs in the 

 teeth, as in the bones, with which they so closely agree in 

 their chemical composition. 



[The apparent walls of the dentinal tubuli, which are com- 

 monly visible in transverse sections (fig. 184), are not the 

 actual walls of the canals, but rings, which result from our 

 invariably viewing a certain length of the canals in the always 

 more or less thick sections, their undulated course giving the 

 walls a greater apparent thickness than they really possess. If 

 in any transverse section the apertures of the canals be exactly 

 brought into focus, we perceive, instead of the dark ring, only a 



