474 SPECIAL HISTOLOGY. 



which, upon close examination, is seen to be composed of a multitude 

 of thin layers, receiving the ends of the contour lines (Fig. 187). They 

 also occur, however, more internally, but always in longitudinal sections, 

 in lines which correspond with the contour lines. The spaces are some- 

 times very wide, intersecting or interrupting in their course many den- 

 tinal canals ; sometimes they are very small, so that only a few canals 

 are touched by them. In the former case, their limits are formed by 

 distinct globular projections of 0-002-0-012 of a line, and more, which 

 are pierced by dentinal canals, and have precisely the same aspect as 

 the dentine, of which they are obviously nothing but portions; whilst 

 in the latter, such dentinal globules, as I will term them, are not always 

 distinct. This is especially true of the smallest spaces, which, on 

 account of their notched form, and their communications with dentinal 

 canals, might be taken for osseous lacunce, and indeed have been so 

 regarded ; yet, at least in the crown, it is almost always easy to recog- 

 nize their identity with the larger spaces. Greater difficulty is met 

 with upon the fang, where small interglobular spaces and globules form 

 a zone (the granular layer of Tomes), which often appears like a layer 

 of small osseous lacunae or of simple granules. I have but rarely 

 observed actual lacunce in normal dentine ; they were, when present, 

 invariably situated at the boundary of the cement (Fig. 185) ; on the 

 other hand, interglobular spaces and dentinal globules are to be met 

 with in the interior of the dentine of the root, and with especial dis- 

 tinctness on the walls of the pulp cavity, in which latter locality the 

 globules often give rise to irregularities visible to the naked eye, or 

 even to a botryoidal appearance. The interglobular spaces whose pre- 

 sence is normal in developing teeth, contain during life, not fluid, as 

 might at first sight be expected, but a soft substance resembling tooth 

 cartilage and possessing a canaliculated structure, like the dentine itself. 

 It is remarkable that this substance offers a greater resistance to long 

 maceration in hydrochloric acid than the matrix of the actually ossified 

 tooth, and therefore, like the dentinal canals, it may be completely 

 isolated. In sections, this interglobular substance usually dries up in 

 such a manner that a cavity is produced, into which air penetrates ; it 

 is properly only in reference to these, that interglobular spaces can be 

 spoken of. Many teeth, indeed, exhibit no interglobular substance, 

 but they occasionally present the outlines of dentinal globules, in the 

 form of delicate arched lines. 



Dentine containing Haversian canals, the so-called " vaso-dentine" 

 of Owen, which exists in many animals, is rarely found in man, and I 

 am only acquainted with one case, observed by Tomes (1. c. p. 225), in 

 which the vascular canals were numerous ; on the other hand, in the 

 dentine with irregular tubuli, which is formed in obliteration of the pulp 

 cavity, we occasionally meet with scattered Haversian canals and 



