442 MR. J. B. SUTTON ON HYPERTROPHY. [AIj^J 5, 



before backwards, and not quite an incb long, and consisted of a 

 small triangular denticle which represented the crown of the tooth, 

 and of a larj;er part, wliich for descriptive purposes may be called 

 the fan"-. Tlie free surface of the denticle was invested with white 

 enamel ; subjacent to the enamel there was a well-defined mass of 

 dentine which constituted the mass of the denticle. The exterior 

 of the fang was coated with a thin layer of cementum, beneath 

 which there was a thin layer of substance consisting of a granular 

 matrix traversed by numerous canals, which were for the most 

 part arranged perpendicularly to the surface of the fang, so as to 

 extend from the dentine to the cementum. Tlie pulp-cavity was 

 lined throughout the greater part of its extent by a well-defined 

 layer of this substance. The canals visible in this substance pro- 

 bably contained blood-vessels ; in size they approximated to Haver- 

 sian canals. This substance in all probability is vaso-dentine. 



Turning, now, to the structural details of an adult specimen of these 

 aberrant teeth, as seen in section (see fig. 8, p. 441), it will become 

 evident, as Prof. Turner has explained, that the peculiar form of this 

 tooth is due to changes in the fang, resulting from an enormous over- 

 growth of cementum and modified vaso-dentine, the former being pro- 

 duced from the alveolo-dentar periosteum, the latter from the pulp. 



My reasons for regarding this singular tooth as a pathological 

 peculiarity are these : — 



1st. The elongated portion of the tooth really consists of the 

 fang, and in many animals, even where the teeth do not grow from 

 persistent pulps, there is a great tendency when the crowns are 

 unopposed for the fangs to elongate (hypertrophy). This condition 

 is often very conspicuous in old horses. 



2nd. The nutritive conditions of the tooth are exceedingly advan- 

 tageous for its hypertrophy : not only is it well supplied from the 

 pulp, but its layers of vaso-dentine place it in suitable relation with 

 the alveolo-dentar periosteum. 



3rd. Judging from the condition of the crown of the tooth, even 

 in adult Whales, it can be subjected to very little friction. Hence 

 the structure, mode of nutrition, and lack of opposition, place this 

 tooth in a very favourable condition to hypertrophy. 



Before dismissing teeth, it will be well to point out how simple a 

 matter it is to show that hypertrophy, especially if it be excessive, 

 must almost of necessity lead to dwarfing of the structures more or 

 less associated with it ; this is particularly well illustrated in the 

 case of the teeth. In man any tooth differs in size but little from 

 those immediately adjacent ; but if, as in the case of rodents, the 

 incisors increase in size, out of all proportion to the neighbouring 

 teeth, their augmentation in volume will lead to a " diversion of the 

 nutrient stream " in their favour, but certainly to the detriment of 

 the teeth immediately succeeding them in the dental series ; and, 

 as a matter of fact, these victimized teeth become so deprived of 

 the essential element-blood, that they remain of stunted size, or 

 have, in some cases, entirely disappeared. It must also be borne in 

 mind that as the incisors increased in size, the effective employment 



