STRUCTURE OF THE DENTAL PULP. 477 



cleus is usually contained in that end which is turned towards 

 the pulp. In adults, as Boll (59) remarks, the form of the 

 cells is very slender, whilst in young teeth they are more or less 

 compressed. Three kinds of processes may be distinguished 

 in these cells. The dentinal process, the pulp process, and the 

 lateral processes. The dentinal processes constitute the above- 

 described dentine fibres ; it need here only be repeated that 

 from one cell several dentine fibres are frequently given off 

 (Boll counted as many as six). Such odontoblasts, with 

 several dentinal processes, are broad at the end, directed to- 

 wards the dentine, but as the processes pass on they gradually 

 diminish to form dentinal fibres. The odontoblasts are inti- 

 mately connected with each other by means of the fine short 

 teeth which the lateral processes of all dentinal cells form. 

 The short pulp process usually springs from the cell with a 

 moderately broad base, and is constantly connected with one 

 of the cells lying immediately beneath the membrana eboris, 

 which last are usually somewhat larger and more darkly 

 granular than those more deeply seated. 



We are indebted to Boll (59) for first furnishing us with precise 

 information in regard to the nerves of the teeth. He observed in the 

 incisor teeth of the Rodents, after the pulp had been macerated for 

 an hour in a solution of chromic acid containing & per cent., a 

 very large number of non-medullated extremely fine nerve fibres, 

 which exhibited a silky lustre, and were gradually but directly con- 

 tinuous with the medullated fibres. If the observer is so fortunate 

 as to preserve the membrana eboris in its natural connection with 

 the pulp, which Boll sometimes accomplished by introducing a fine knife 

 between the pulp and the dentine, after treatment with chromic acid, 

 the extraordinary richness of these non-medullated fibres in the peri- 

 pheric portions of the pulp becomes apparent. Preparations that 

 have been teased out with needles show that the nerve fibres pass 

 outwards between the odontoblasts in considerable numbers, and 

 accompany the dentinal processes to which they are subjacent in the 

 form of fine hairs. Boll was, however, unable to see the actual 

 penetration of the nerve fibres into the dentinal tubuli, although their 

 length and the direction they pursued rendered this probable. 



The gum is distinguished from the other portions of the 

 oral cavity by its vascularity and its large papillae, which 



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