THE TEETH. 497 



portions become obliterated bj deposits, or the pulp is protected by new 

 masses of dentine developed in the cavity* (Ficinus, Tomes). Eventually 

 a brownish deposit takes place in the tubules and then the intermediate 

 substance becomes completely broken up. In this manner the process 

 of decomposition extends further and further, until at last the crown 

 collapses, the root also becoming dissolved and finally falling out. 



In jaundice, the teeth not uncommonly assume a yellow color, which 

 is occasionally almost as intense as in the skin, and in asphyxiated per- 

 sons they are said frequently to be red ; both facts being explicable only 

 by the supposition that the coloring matter of the bile and of the blood 

 transudes into the dentinal tubuli. In rachitis the teeth remain unaf- 

 fected. In the mucus upon the teeth, an abundant growth of the muce- 

 dinous fungi which have been mentioned, is always to be met with in a 

 finely granular matrix, surrounding mucus- or epithelium-corpuscles ; 

 besides w"hich we find the infusoria of carious teeth and the earthy 

 deposits of the oral fluids. If this mucus accumulates, it hardens and 

 forms the tartar of the teeth, which consists, according to Berzelius, of 

 earthy phosphates 79-0, mucus 12*5, ptyalin 1"0, organic matter, soluble 

 in hydrochloric acid, 7"0. 



The best mode of examination of the teeth is by making fine sections 

 and preparations softened in hydrochloric acid. To obtain good speci- 

 mens of the former it is necessary to employ only young and fresh teeth, 

 as the enamel otherwise readily breaks off. A longitudinal or trans- 

 verse slice should be first taken off with a fine saw, and may then be 

 rubbed down, first upon a coarser and then upon a finer stone, as thin 

 as possible ; the section should then be cleaned and polished between 

 two glass plates, until its surface is as smooth and shining as it can be 

 made, and finally washed with ether in order to remove any impurities 

 it may have contracted. When well polished and dried, all the dentinal 

 canals and lacutue will be filled with air, and the section may be pre- 

 served without further addition under a glass plate, cemented by some 

 thick and quickly solidifying varnish. Such polished sections are pre- 

 ferable to any others, which, on account of their irregular surface, re- 

 quire to be covered with different fluids, as Canada balsam, oil of tur- 

 pentine, &c., in order to be examined by high magnifying powers. It 

 almost always happens, in fact, that some portion of these fluids enters 

 the dentinal tubules, which then become quite clear and indistinct and 

 invisible in their finer ramifications. A very viscid varnish alone is of 

 any service. In preparing these sections of the teeth, the slices may 



* ["It is worthy of mention, also, that in the teeth of the liare, the sow, and the stag, 

 especially in the molars, stony masses are constantly found. They are semi-transparent, for 

 the most part oval and rounded bodies, situated in the axis of the dental pulp, towards its 

 apex, in irregular rows, never extending the whole length of the dental pulp, but only to a 

 greater or less distance from the coronal extremity." Raschkow, Meletemata, &c., cited and 

 translated in Nasmyth's " Researches'' (1839), p. 139. — Trs.] 



32 



