332 DR W. G. AITCHISON ROBERTSON ON THE RELATION OF 



III. The third rabbit was also fed on madder for two weeks, then on ordinary food 

 for three weeks. The teeth show merely a further development of what No. II. did 

 (Fig. 16). The sections hardly require explanation, as they describe themselves. These 

 madder-stained teeth corroborate entirely the explanation of the growth of the dentine 

 which I have already given. 



The results of this investigation into the growth of teeth may be thus summarised. 

 There is — 



(1) Increase in the length of the tooth by addition of new dentine at its base. 



(2) Increase of diameter by dilatation of the basal formative ring. In the case of 

 teeth with fangs, these are produced by the gradual contraction of this ring with or 

 without subdivision. 



(3) Deposit of new dentine on the inner surface of the old. 



(4) A slight increase in the matrix of the dentine by interstitial growth. 



I have in conclusion to express my warm thanks to Professor Rutherford for the free 

 use of his laboratory, microscopical preparations, and other appliances, and for his careful 

 revision of this paper, and to Professor Haycraet, who suggested this subject for research 

 and who supervised my work personally and helped me with many suggestions in the 

 execution of it. 



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Nasmyth, Med. Chirurg. Transact, 1839, vol. xxii. 



Goodsir, Prof., "On the Origin and Development of the Pulp and Sacs of the Human Teeth," Edin. Med. 

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