Chap. XII. 



INHERITANCE. 



13 



to me, of forty-six persons with extra digits on one or both hands and 

 feet ; if in each case all fonr extremities had been similarly affected, the 

 table would have shown a total of ninety-two hands and ninety-two feet 

 each with six digits. As it is, seventy-three hands and seventy-five feet 

 were thns affected. This proves, in contradiction to the result arrived at 

 by Dr. Struthers, 27 that the hands are not more frequently affected than 

 the feet. 



The presence of more than five digits is a great anomaly, for this num- 

 ber is not normally exceeded by any mammal, bird, or existing reptile. 28 

 Nevertheless, supernumerary digits are strongly inherited; they have 

 been transmitted through five generations ; and in some cases, after 

 disappearing for one, two, or even three generations, have reappeared 

 through reversion. These facts are rendered, as Professor Huxley has 

 observed, more remarkable from its being known in most cases that 

 the affected person had not married one similarly affected. In such cases 

 the child of the fifth generation would have only l-32nd part of the blood 

 of his first sedigitated ancestor. Other cases are rendered remarkable 

 by the affection gathering force, as Dr. Struthers has shown, in each 

 generation, though in each the affected person had married one not affected; 

 moreover such additional digits are often amputated soon after birth, and 

 can seldom have been strengthened by use. Dr. Struthers gives the following 

 instance : in the first generation an additional digit appeared on one hand ; 

 in the second, on both hands ; in the third, three brothers had both hands, 

 and one of the brothers a foot affected ; and in the fourth generation all 

 four limbs were affected. Yet we must not over-estimate the force of 

 inheritance. Dr. Struthers asserts that cases of non-inheritance and of the 

 first appearance of additional digits in unaffected families are much more 

 frequent than cases of inheritance. Many other deviations of structure, 

 of a nature almost as anomalous as supernumerary digits, such as deficient 

 phalanges, thickened joints, crooked fingers, &c, are in like manner strongly 

 inherited, and are equally subject to intermission with reversion , though 

 in such cases there is no reason to suppose that both parents had been 

 similarly affected. 29 



27 ' Edinburgh New Phil. Journal,' 

 July, 1863. 



28 Some great anatomists, as Cuvier 

 and Meckel, believe that the tubercle 

 on one side of the hinder foot of the 

 tailless Batrachians represents a sixth 

 digit. Certainly, when the hinder foot 

 of a toad, as soon as it first sprouts 

 from ihe tadpole, is dissected, the par- 

 tially ossified cartilage of this tubercle 

 resembles under the microscope, in a 

 remarkable manner, a digit. But the 

 highest authority on such subjects, 

 Gegenbaur (Untersuchung zur ver- 

 gleich. anat. der Wirbelthiere : Carpus 

 et Tarsus, 1864, s. 63), concludes that 



this resemblance is not real, only super- 

 ficial. 



29 For these several statements, see 

 Dr. Struthers, in work cited, espe- 

 cially on intermissions in the line of 

 descent. Prof. Huxley, ' Lectures on 

 our Knowledge of Organic Nature,' 

 1863, p. 97. With respect to inheritance, 

 see Dr. Prosper Lucas, ' L'Heredite' Nat./ 

 torn. i. p. 325. Isid. GeofFroy, ' Acorn.,' 

 torn. i. p. 701. Sir A. Carlisle, in ' Phil, 

 Transact.,' 1814, p. 94. A. Walker, on 

 'Intermarriage,' 1838, p. 140, gives a 

 case of five generations ; as does Mr. 

 Sedgwick, in ' Brit, and Foreign Medico- 

 Chirurg. Review,' April, 1863, p. 462. 



