1885.] MR. J. B. SUITON ON HYPERTROPHY. 431) 



fisher, with thirty years' experience of this loch, has never taken any 

 but docked ones. 



It seems to me that these fish clearly inherit their deformity, and 

 that it is a perpetuated pathological condition. 



Returning to teeth, there can be little doubt that a similar process 

 has been at work modifying the singularly aberrant tusks of the 

 Narwhal, Monodon monoceros. Its huge size, the curious spiral 

 twist, undoubtedly correlated with the peculiar unsynunetrical con- 

 dition of the facial portion of the skull found in this Whale as well 

 as among other members of the Physeteridse, tend to support the 

 notion of a pathological cause miderlying these monstrosities. 



In this singular creature the adult male usually possesses a tooth 

 growing from the left maxillary bone, in close relation with the 

 niaxillo-jjremaxillary suture and therefore regarded as a canine, 

 which often attains a length of eight, nine, or even ten feet, with a 

 basal diameter of four inches. Tlie corresponding tooth of the 

 opposite side usually undergoes development up to a certain point, 

 and attains a size of six inches, but the pulp-chamber usually under- 

 goes calcification before it has had time to make its way out of the 

 alveolus, so that it remains concealed througho>it the lifetime of the 

 animal. Occasionally, however, this right tusk undergoes develop- 

 ment, and equals in size the left one. Mr. J. W. Clark communicated 

 to this Society in 18/1 the results of an inquiry into the matter 

 of double-tusked Narwhals, and has given in that very interesting 

 paper details of no less than eleven bidental skulls of this Whale in 

 different European Museums \ This seems to afford evidence that 

 normally the Narwhal should possess two teeth, but that from some 

 cause or other the right one often remains suppressed in the alveolus ; 

 and there is the significant fact, pointed out by Mr. Clark, that 

 v.henever a solitary tooth is present it is the left one, the right 

 never being developed alone. The spiral twist in connection with these 

 tusks always winds round them from right to left ; if two tusks be 

 developed, the twist of the spiral is in the same direction in both, 

 as regards the skull right to left, whereas they appear utisymmetrical 

 in respect to one another. There can be little doubt that this 

 curious twist in the tusks is the effect of the same cause, what- 

 ever it may be, that produces the remarkable distortion in the facial 

 portion of' the skull of these whales. Prof. Flower has described, 

 in the Trans. Odont. Soc. 1879-80, some curious Elephants' tusks 

 contained in the Museum of the College of Surgeons. These tusks 

 ire spirally twisted, the twist possessing in some instances two or 

 more turns : a deej) groove extends from base to apes. In this 

 instance it is clear that the malformation resulted from injury to the 

 growing pulp when the tooth was in embryo. There is no just 

 reason why the same line of argument should not be aj)plied to the 

 Narwhal tooth. The tusk has yet other interest for the pathologist. 

 Professor Turner was fortunate enough to detect in the skull of a 

 fcetai Narwhal two rudimentary teeth, all traces of which are lost in 



» See r. Z. S. 1871, p. 42. 



29* 



