BOWMAN LECTURE. LXXXIII 



chiefly with the larger specimens of lamellar cataract that 

 the well-known and characteristic deficiency of enamel in 

 the permanent incisors and first molars is found, and Mr. 

 Norman G. Bennett, after careful consideration of the 

 evidence in connection with the date of formation of the 

 enamel, has come to the conclusion that the cause of the 

 deficiency is active from shortly after birth until about 

 two years of age;"* and that the correlated lenticular 

 change is probably not ante-natal. He points out that 

 the epiblastic elements of both lens and enamel become 

 isolated within mesoblastic tissue, and that both might 

 therefore not improbably be affected by a common cause 

 of malnutrition. 



Now I have myself often noticed that in cases of 

 unusually small lamellar cataract (as well as in its 

 minimal discoid variety), there is usually no defect of 

 the enamel of the permanent teeth. This fact comes out 

 strongly in all the extensive pedigrees of lamellar cataract 

 hitherto published, for in these the opacity is almost in- 

 variably small and the teeth good.t 



The conclusion, therefore, is that when lamellar 

 cataract is hereditary the small size of the lenticular 

 opacity, and the absence of dental deformity, both point 

 to the cataractous change having occurred during intra- 

 uterine life. It has been assumed that the visible results 

 lack of enamel for the permanent teeth and lamellar 

 opacity in the lens mark the commencement of the 

 morbid process, but this can hardly be true, at least for 

 the lens ; something is probably wrong both in the lens 

 and the uncalcified enamel before we can detect any 



* Norman G Bennett, " Etiology of Lamellar Cataract," T.O.8., xxi, 

 1901, p. 42. 



t Exceptions are, of course, seen, but I believe they are not very 

 frequent or very well marked. See R.L.O.H., xvi, p. 231, Case 74 

 and Case 75,1 (Elizabeth). On the contrary, for confirmation of the 

 general statement see Cases 72, 74 (mother), and 76, 5 (Louisa). The 

 point is also illustrated in Fig. 12 (from T.0.8 , xxviii, p. 226), where 

 the only one (IV, 102) with large lamellar cataract had the character- 

 istic teeth, whilst the teeth were normal in those with small-sized 

 cataract. 



