668 



THE TEETH. 



We recognize, under the microscope, in longitudinal section of the dentine, 

 that sometimes the yellow discoloration has taken place only within the lim- 

 its of a few dentinal canaliculi, while at other times quite a number of these 

 have undergone discoloration. Still sharper denned is the yellow discoloration 

 on transverse sections. Here we see that mainly the canaliculi and their 

 immediate neighborhood have taken up the yellow color in the shape of 

 sharply circumscribed dots, which are the larger the nearer they approach to 

 the periphery of the decayed part. The basis-substance between these yellow 

 spots has taken up more or less carmine. (See Fig. 293.) 



At a certain distance from the decay the canaliculi look unchanged, and 

 each contains the central transverse section of the dentinal fiber, with its del- 

 icate radiated offshoots. Nearer to the decay we meet with moderately 



FIG. 294. CARIES OF DENTINE. OBLIQUE SECTION. 



P, widened dentinal canaliculus, containing bioplasson ; N, space containing medullary 

 corpuscles ; -^.transformation of dentine into bioplasson; C, trace of deiitinal caualiculus 

 containing an enlarged fibril. Magnified 1000 diameters. 



enlarged canaliculi, the center of which is occupied by a cluster of bioplasson, 

 the granules and threads of which have readily taken up the carmine. One 

 step farther we find the. canaliculi considerably enlarged to double or treble 

 their original size and they are filled with bioplasson, plainly exhibiting the 

 net-like arrangement of the living matter. The most peripheral granules send 

 delicate conical offshoots through the surrounding light space toward the 

 unchanged basis-substance. In some of the enlarged canaliculi accumula- 

 tions of living matter are seen fully in the shape of nuclei ; sometimes two or 

 more such nuclei may be seen surrounded by a varying amount of granular 



