o 



NATURE 



[Sept. 26, 188^ 



genital deaf-mutism, in the great irajority of instance?, is 

 associated with a defective development, and therefoie a 

 structural variation of the organ of hearing, though in some 

 cases, perhaps, the defect may be in the development of the 

 brain itself. 



Although a sufiicitnt number of cases has now been put on 

 record to piove that in seme families one or other kind of con- 

 genital deformity may be hereditarily transmitted, yet I do not 

 wish it to be su) posed that congenital malformations may not 

 arise in individuals in whom no hereditary tendency can be 

 traced. It is undoubtedly true that family histories are in many 

 cases very defective, and frequently cannot be followed back for 

 more than one, or, at the m.ost, two generations ; so that it is 

 not unlikely that an hereditary predisposition may exist in many 

 instances where it cannot be proved. Still, allowing even for a 

 considerable proportion of such cases, a sufficient number will 

 remain to warrant the statement that malformations or variations 

 in stiucluie which have not been displayed by their ancestors 

 may arise in individuals belonging to a particular generation. 



The variations which I have spoken of as congenital malfor- 

 mations arise, as a rule, before the time of birth, during the early 

 development of the individual ; but there is an important class of 

 cases, in which the evidence for hereditary transmission is more 

 or less strong, which may not exhibit their peculiarities until 

 months, or even years, after the birih of the individual. This 

 class is spoken of as hereditary diseases, and the structuial and 

 functional changes which they produce exercise most momentous 

 influences. Sometimes these diseases may occasion changes in 

 the tissues and organs of the body of considerable magnitude, 

 but at other times the alteration is much more subtle, is mole- 

 cular in its character, requires the microscope for its determina- 

 tion, or is even incapable of being recognized by that instru- 

 ment. 



Had one teen discussing the subject of hereditary disease 

 twenty years ago, the first example probably that would have 

 been adduced would have been tuberculosis, but the additions to 

 our knowledge of late ytars throw some doubt upon its here- 

 ditary character. Thtre can, of course, be no question that 

 tubercular disease propagates itself in numerous families from 

 generation to geneiation, and that such families show a special 

 susceptibility or tendency to this disease in one or other of its 

 forms. But whilst fully admitting the predisposition to it which 

 exists in certain families, there is reason to think that the struc- 

 tural disease itself is not hereditarily transmitted, but that it is 



directly excited in each individual in whom it appears by a 

 process of external infection due to the action of the tubercle 

 bacillus. Still, if the disease itself be not inherited, a particular 

 temperament which renders the constitution liable to be attacked 

 by it is capable of hereditary transmission. 



Sir James Paget, ^ when writing on the subject of cancer, gives 

 statistics to show that about a quarter of the persons affected 

 were aware of the existence of the same disease in other mem- 

 bers of their family, and he cites particular instances in which 

 cancer was present in two and even four generations. He had 

 no doubt that the disease can be inherited — not, he says, 

 that, strictly speaking, cancer or cancerous material is trans- 

 mitted, but a tendency to the production of those conditions 

 which will finally manifest themselves in a cancerous growth. 

 The germ from the cancerous parent must be so far different 

 from the normal as after the lapse of years to engender the 

 cancerous condition. 



Heredity is also one of the most powerful factors in the pro- 

 duction of those affections which we call gout and rheumatism. 

 Sir Dyce Duckworth, the latest systematic writer on gout, states 

 that in those families whose histories are the most complete and 

 trustworthy the influence is strongly shown, and occurs in from 

 50 to 75 per cent, of the cases ; further, that the children of 

 gouty parents show signs of articular gout at an age when they 

 have not assumed those habits of life and peculiarities of diet 

 which are regarded as the exciting causes of the disease. 



Some interesting and instructive family histories, in which the 

 hereditary transmission of a particular disease through several 

 generations has been worked out, are recorded by Prof, Klebs 

 in his "Allgemeine Pathologic." I may draw from these one 

 or two additional illustrations. Some families exhibit a re- 

 markable tendency to bleed when the surface of the body is 

 injured or bruised, and the bleeding is stopped with difficulty. 

 The hsemorrhagic tendency is not due to the state of the blood, 

 but to a softening or degeneration of the walls of the blood- 

 vessels, so that they are easily torn. In one family, the tree of 

 which is here subjoined, this peculiarity showtd itself in one 

 generation in three out of four males ; in the next generation, in 

 thirteen out of fourteen males ; whilst in the immediately succeed- 

 ing generation only one out of nine males was affected ; so that it 

 would seem as if the tendency was fading away in it. It is re- 

 markable that throughout the series, though the transmission of 

 the affection went through the female members, they themielves- 

 remained free from it. 



The bleeding jamily Mampel, recorded by Dr. Lessen. 



M F 



I i 



M 



M F 



F M M M F M M 



M 



Fi 



M 



m: 



I 



M M M F 



I 

 M 



I I 



F M M F MM 



M F 



M F 



M F M F 



M F 



M F 



M F F M F 



M F 



Another illustration maybe taken from the well-known disease 

 of the eyeball called cataract. Dr. Appenzeller has given an 

 account of a family which exhibited so strong a tendency to this 



affection that the males were affected in four generations, though 

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

 family tree. 



M 



M 



M 



M 



I 



M 



I 



M 



F 



M 



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

 lesion itself is transmitted, but that the tendency or predisposi- 

 tion to produce it is inherited. The germ-plasm, therefore, in 

 these individuals must have been so modified from the normal as 



I to carry with it certain peculiarities, and to induce the particular 

 form of disease which showed itself in each family. 



' " Lectures on Surgical Pathology," third erii:ion, revised and edited 

 by the author and W. Turner (London, 1870). 



