TRANSACTIONS OF SECTION H. 765 



losis, but the additions to our knowledge of late years throw some doubt upon its 

 hereditary character. There can, of course, be no question that tubercular disease 

 propagates itself in numerous families from generation to generation, 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 predispo.sition to it which exists in certain 

 families, there is reason to think that the structural di.sease itself is not hereditarily 

 transmitted, hut 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 members 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 transmitted, but a tendency to the production of those con- 

 ditions which will finally manifest themselves in a cancerous growth. The germ 

 from the cancerous parent must be so far difi'ereut 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 production 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 sliowu, 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 halnts 

 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 Professor Klebs in his ' Allgemeine Pathologic.' I mnv draw 

 from these one or two additional illustrations. Some families exhibit a remark- 

 able tendency to bleed when the surface of the body is injured or bruised, and the 

 bleeding is stopped with dithculty. The hemorrhagic 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 liere 

 subjoined, this peculiarity showed itself in one generation in three out of four 

 males; in the next generation, in thirteen out of fourteen males; whilst in the 

 immediately succeeding 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 remarkable that 

 throughout the series, though the transmission of the affection went throun-h the 

 female members, they themselves remained free from it. 



The Family Mampel, recorded by Dr. Zosscn. 

 M F 



I I 



I 



I II I II 



M F M F IVI M 



I 



II I I I I II I I I I I I I I I I I I I I 



>IF FMMMFMMF F M MM F m fmMfmmf 



_L L _l ± L J I _i ___! I 



II 1 I I I II I I i 1 I I "1 I I I n 



M F M F M F M F M F M F F M F F M F MP 



Another illustration may be taken from the well-known disease of the eyeball 



' Lecturrit on Siiryiral Pathohgy, 3rd cd., revised and edited by the author and 

 W. Turner, London, 1870. 



