690 REPOBT— 1886. 



In all the laterals are the missing teeth. The jaws are generally well formed, and 

 there are often gaps between the teeth in the incisor region. The ages of four of 

 these patients were 21, 22, 22, and 17 respectively ; of the others we have no 

 exact information, but they were adults. 



The points which these cases illustrate are as follows : — 



(i.) Mmi's original dentition included six incisors. — This thesis is already fairly 

 generally admitted by odontologists. If supplemental and supernumerary teeth are 

 to be regarded as reversions to the primitive dentition, then in two cases we have, 

 so far as the superior maxilla is concerned, the complete series. Galton, Wilson, 

 Flower, and Edwards also quote cases of six incisors in the upper jaw. Kirk de- 

 scribes one which occurred in the inferior maxilla and in the milk series. As Wedl 

 remarks, however, the occurrence of six incisors is rare. That of five is, on the 

 contrary, fairly common. "What has just been said relates to supplemental teeth, 

 but, as will be seen by a reference to the digest of the series above, a supple- 

 mental and supernumerary may coexist to increase the number of the dentition to 

 six, or two or one supernumeraries may coexist with the normal four incisors. 

 That a milk supplemental may be followed by a permanent successor is proved by 

 a case for which we are indebted to Mr. Amoore. This is interesting as bearing on 

 the development of these teeth. We may sum up by saying that man seldom 

 attains to the archaic dentition of In | in the upper jaw, still more rarely in the 

 lower, never, so far as we are aware, in both simultaneously. On the other hand, 

 in fairly numerous cases, he regains one of his lost teeth, either ill- or well-formed, 

 or both, in an imperfectlj^ formed condition. 



(ii.) Man's lost incisor is the lateral or In^. — Baume and Edwards consider the 

 lost tooth to be In,, mainly on account of a supposed separation existing between 

 the two median. This separation is, in our experience at least, by no means 

 common. Again, in all our cases, whatever teeth are added or suppressed, the 

 medians remain typical in shape. We have also casts showing that the ordinary 

 laterals may take up a position behind the median. This shows that teeth found 

 in this position need not necessarily be abortive medians. These facts, we be- 

 lieve, dispose of the median theory. Two other arguments, shortly to be men- 

 tioned, also make against it. Turner and Wilson's theory, that the niissing incisor 

 is In.-,, is much more tenable. We are unable at present to explain the facts quoted 

 by the former authority, but would venture to put forward the following arguments 

 in support of our position : — 



1. Tomes bases his theory that the dentition of man was In | on the fact that 

 Homalodontotherium possessed that nimiber of teeth, and that the transition from 

 incisors to canine was thus rendered more gradual. Upon these grounds he be- 

 lieves that lug is the lost tooth. Now, if we suppose that luj or In^ is missing 

 the force of this argument falls to the groimd, unless we believe that, pari passu 

 with their suppression, the others became modified in shape, which there are not 

 facts to prove. 



2. It has long been held — and we have fresh facts to show its truth — that the 

 present lateral incisor is now being suppressed. This being so, it seems more reason- 

 able to suppose that the tooth already lost is that which lay behind the present 

 lateral in the original series. 



3. Finally — and this is the most important argument — wherever the dentition 

 is increased by two or one incisors, the superadded teeth are behind the laterals, that 

 is, are lUg. This is shown in the case where six are present, and still better in 

 one case of five, where the superadded tooth is obviously In,, has no fellow on the 

 opposite side, and affords a perfect example of a tooth bridging over the gap 

 between incisors and canine. 



(iii.) The loss of incisors is due to the contraction of the anterior parts of the jaw. 

 — It is well known that the jaws of civilised races are less well developed than those 

 of uucivihsed, and that amongst the former the lower have better shaped alveolar 

 arches than the upper classes. These facts are dealt with by Darwin, Herbert 

 Spencer, Oakley Coles, Cartwright, Coleman, Mummery, and Mcholls. We have 

 not had an opportunity of working out the poii:t satisfactorily, but believe this 

 contraction to take place most markedly in the incisive region. Topinard states 



