244 THE INDUCTIONS OF BIOLOGY. 



spared. Defects in the organs of sense are also not 



unfreqnently inherited. Four sisters, their mother, and 

 grandmother, are described by Duval as similarly affected by 

 cataract. Prosper Lucas details an example of hereditary am- 

 aurosis affecting the females of a family for three generations. 

 Duval, Graffe, Dufon, and others testify to like cases coming 

 under their observation.* Deafness, too, is occasionally trans- 

 mitted from parent to child. There are deaf-mutes whose 

 imperfections have been derived from ancestors ; and mal- 

 formations of the external ears have also been perpetuated in 

 offspring. Of transmitted peculiarities of the skin 



and its appendages, many illustrations have been noted. One 

 is that of a family remarkable for enormous black eyebrows ; , 

 another that of a family in which every member had a lock of 

 hair of a lighter colour than the rest on the top of the head ; 

 and there are also instances of ^congenital baldness being 

 hereditary. Entire absence of teeth, absence of particular 

 teeth, and anomalous arrangements of teeth, are recorded as 

 traits that have descended to children. And we have evidence 

 that soundness and unsoundness of teeth are transmissible. 



The inheritance of such diseases as gout, consumption, and 

 insanity, is universally admitted. Among the less-common 

 diseases of which the descent from one generation to another 

 has been observed, are, ichthyosis, leprosy, pityriasis, sebace- 

 ous tumours, plica polonica, dipsomania, somnambulism, cata- 

 lepsy, epilepsy, asthma, apoplexy, elephantiasis. General 

 nervousness displayed by parents, almost always re-appears 

 in their children. Even a bias towards suicide appears to 

 be sometimes hereditary. 



§ 82. To prove the transmission of those structural pecu- 

 liarities that have resulted from functional peculiarities, is, 



* While this chapter is passing through the press, I learn from Mr White 

 Cooper, that not only are near sight, long sight, dull sight, and squinting, he«re- 

 ditary ; "but that a peculiarity of vision confined to one eye, is frequently trane 

 rjnitted — re- appearing in the same eye in offspring. 



