THE TEETH. 



489 



Fig. 197. 



form, resembles the tooth to which it belongs, and consists of an internal 

 portion rich in vessels, and eventually in nerves also, and of a non- 

 vascular external portion. The latter is bounded by a delicate structure- 

 less membrane, the membrana prceformativa (Raschkow), which has no 

 further relation to the development of the tooth. Beneath this, lie 

 cells of 0-016-0-024 of a line in length, and 0-002-0-0045 of a line in 

 breadth, with very beautiful, vesicular nuclei, and distinct, single or 

 multiple nucleoli ; they are arranged close together over the whole 

 surface of the pulp (Fig. 197), like an epithelium, though not so sharply 

 defined internally as it would be, but 

 gradually passing, at least apparently, 

 by smaller cells, into the parenchyma. 

 In vascular pulps (Fig. 197), an addi- 

 tional boundary line may be traced, inas- 

 much as the capillary loops in which the 

 vessels terminate, do not penetrate be- 

 tween the cylindrical cells, but end close 

 to one another upon their inner surface ; 

 so that, considering that the dentine is 

 produced by the cells in question, we 

 might be justified in terming them the 

 dentinal membrane, or membrana eboris. 

 The internal portions of the pulp consist 

 throughout of an originally granular or homogeneous, afterwards more 

 fibrous matrix, containing many rounded or elongated nuclei, w r hich 

 must be regarded as a sort of connective tissue. Vessels are developed 

 in great numbers in the pulp at the period when ossification commences ; 

 the most numerous perpendicular loops of capillaries of about 0-006 of 

 a line existing in contiguity with the ossifying surface. The nerves 

 accompany the vessels, but are developed later ; their number is very 

 considerable and their distribution resembles that in the pulp of the 

 perfect tooth. 



The enamel organ (organ adamantince), is applied to the pulp like a 

 cap by its internal, concave surface, and is connected externally with 

 the dental sac, in such a manner, however, that at the base of the pulp 

 it presents a very small free edge. Its structure is very peculiar. The 

 principal mass consists of anastomosing stellate cells (Fig. 196, 5), or 

 reticulated connective tissue, containing in its meshes a great quantity 

 of fluid, rich in albumen and mucus. This gelatinous connective tissue 

 is most abundant immediately before the commencement of ossification, 

 and in its earliest stages. Thus, in the fifth and sixth months it mea- 

 sures T V-3 of a line ; in the new-born infant, on the other hand, only 



FIG. 197. Surface of the dentinal pulp of a newly-born infant: a, dentinal cells; 6, their 

 appendages; c, vascular part of the pulp ; magnified 300 diameters. 



