66 SPECIAL HISTOLOGY. 



connective tissue is most abundant immediately before the 

 commencement of ossification, and in its earliest stages. 

 Thus, in the fifth and sixth months it measures -^ — § of a line ; 

 in the new-born infant, on the other hand, only 0*16 — 02'". 

 At this period it contains vessels in its outer third and its 

 network is metamorphosed into true connective tissue, (Mikr. 

 Anat. ii, fig. 211.) On the inner side of the spongy tissue 

 of the enamel organ, lies the so-called enamel membrane, mem- 

 brana adamantine (Raschkow), a true cylinder epithelium, of 

 which it need only be said that its cells measure 001 2'" in 

 length, and 0*002 /// in breadth, are finely granular and delicate, 

 and possess nuclei frequently situated at the ends of the cells. 



The development of the dental tissues has, hitherto, always 

 been regarded as a very difficult subject. The simplest rela- 

 tions are presented in the enamel, where there can be no doubt 

 whatever that the enamel-cells become, by their complete ossi- 

 fication, the enamel-fibres. As soon as only a small portion of 

 the cells has become ossified (without the previous deposit of 

 calcareous matter in a granular form), a little scale of enamel 

 is recognizable upon the somewhat larger cap of dentine, which 

 has also just been produced. The deposition of calcareous 

 matter in the cells constantly advances outwards, until at last 

 they are entirely converted into enamel fibres, and extends at 

 the same time to other cells, so that the layer of enamel increases 

 in width. During this process, the enamel membrane does 

 not disappear in the locality in which ossification commenced, 

 but retains, there and elsewhere, the same thickness, so long as 

 the deposition of enamel continues; its ossifying part, there- 

 fore, must be replaced by the incessant development of new 

 substance, which takes place apparently, not by the apposition 

 of new cells, but by the continual growth of the old ones. The 

 enamel organ has assuredly some very important relation to the 

 development of the enamel ; probably serving by the abundance 

 of albumen and of mucus in its meshes, as a storehouse, out of 

 which the enamel membrane, distant as it is from blood- 

 vessels, is enabled to draw the materials for its increase. In 

 fact, the spongy tissue is seen to decrease more and more 

 during the development of the enamel, and finally, when the 

 enamel is complete, to disappear. 



In the development of the dentine, as in that of the enamel, 



