766 KEPOET — 1889. 



called cataract. Di'. Appenzeller has given an account of a family whicli exhibited 

 so strong a tendency to this affection that the males were affected in four genera- 

 tions, though the females did not entirely escape, as is shown in the subjoined 

 family tree. 



M 



F M 



IVI FFFFFFM 



M M F F F F M 



In neither of these families can it be said that the structural lesion itself is 

 transmitted, but that the tend«^ncy or predisposition to produce it is inherited. The 

 "■erm-plasm, therefore, in these individuals must have been so modified from the 

 normal as to carry with it certain peculiarities, and to induce the particular form of 

 disease which showed itself in each family. 



In connection with the tendency to the transmissibility of either congenital 

 malformations, or diseases, consanguinity in the parents, although by no means a 

 constant occurrence, is a factor whicli in many cases must be taken into considera- 

 tion.i If we could conceive both parents to be physiologically perfect, then it 

 may be presumed that the offspring would be so also ; but if there be a departure 

 in one parent from the plane of physiological perfection, then it may safely be 

 assumed that either the immediate offspring or a succeeding generation will display 

 a corresponding departure in a greater or less degree. Should both parents be 

 physiologically imperfect, we may expect the imperfections if they are of a like 

 nature to be intensified in the children. It is in this respect, therefore, that the 

 risk of consanguineous marriages arises, for no family can lay claim to physiological 

 perfection. 



When we speak of tendencies, susceptibilities, proclivities, or predisposition to 

 the transmission of characters, whether they be normal or pathological, we employ 

 terms which undoubtedly have a certain vagueness. We are as yet quite unable 

 to recognise, by observation alone, in the germ-plasm any structural change which 

 would enable us to say that a particular tendency or susceptibility will be mani- 

 fested in an organism derived from it. We can only determine this by following 

 out the life-history of the individual. Still it is not the less true that these terms 

 express a something of the importance of which we are all conscious. So far as 

 Man is concerned, the evidence in favour of a tendency to the transmission of both 

 structural and functional modifications which are either of dis-service, or positively 

 injurious, or both, is quite as capable of proof as that for the transmission of cha- 

 racters which are likely to be of service. Hence useless as well as useful characters 

 may be selected and transmitted hereditarily. 



I have dwelt somewhat at length on the transmissibility of useless characters, 

 for it is an aspect of the subject which more especially presents itself to the notice 

 of the pathologist and physician ; and little, if at all, to that of those naturalists 

 whose studies are almost exclusively directed to the examination of organisms in 

 their normal condition. But when we look at Man, his diseases form so large a 

 factor in his life that they and the effects which they produce cannot be ignored 

 in the study of his nature. 



Much has been said and written during the last few years of the transmission 

 from parents to offspring of characters which have been ' acquired ' bj^ the parent, 

 80 that I cannot altogether omit some reference to this subject. It will conduce 



> I may especially refer for a discussion of this subject to an admirable essay by 

 Sir Arthur Mitchell, K.C.B., On Blood Relationship in Marriage considered in, its 

 Influence upon the Offspring. 



