54 INHERITANCE. Chap. XIV 



than the foregoing cases, because diseases are not necessarily con- 

 nected with any change in structure ; but in other respects of more 

 value, because the periods have been more carefully observed. 

 Certain diseases are communicated to the child apparently by 

 a j)rocess like inoculation, and the child is from the hrst affected ; 

 such cases may be here passed over. Large classes of diseases 

 usually appear at certain ages, such as St. Titus's dance in youth, 

 consumption in early mid-life, gout later, and apoplexy still later ; 

 and these are naturally inherited at the same period. But even in 

 diseases of this class, instances have been recorded, as with St. 

 Vitus's dance, showing that an unusually early or late tendency to 

 the disease is inheritable.^^ In most cases the appearance of any 

 inherited disease is largely determined by certain critical periods 

 in each person's life, as well as by unfavourable conditions. There 

 are many other diseases, which are not attached to any particular 

 period, but which certainly tend to appear in the child at about 

 the same age at which the i3arent was first attacked. An array of 

 high authorities, ancient and modern, could be given in support of 

 this proposition. The illustrious Hunter believed in it; and Piorry"*^ 

 cautions the physician to look closely to the child at the period 

 when any grave inheritable disease attacked the parent. Dr. 

 Prosper Lucas;'''^ after collecting facts from every source, asserts 

 that affections of all kinds, though not related to any particular 

 period of life, tend to reappear in the offspring at whatever period 

 of life they first appeared in the progenitor. 



As the subject is important, it may be well to give a few 

 instances, simply as illustrations, not as proof; for jDroof, recourse 

 must be had to the authorities above quoted. Some of the 

 following cases have been selected for the sake of showing that, when 

 a slight departure fi'om the rule occurs, the child is affected some- 

 what earlier in life than the parent. In the family of Le Compte 

 blindness was inherited through three generations, and no less 

 than twenty-seven children and grandcliildren were all affected at 

 about the same age; their blindness in general began to advance 

 about the fifteenth or sixteenth year, and ended in total deprivation 

 of sight at the age of about twenty- two.^^ In another case a father 

 and his four children all became blind at twenty-one years old ; in 

 another, a grandmother grew blind at thirty-five, her daughter at 

 nineteen, and three grandchildren at the ages of thirteen and eleven.^^ 



^* Dr. Prosper Lucas, ' Hered. Nat.,' children and grandchildren is given 



torn. ii. p. 713. as 37 ; but this seems to be an error 



^^ ' L'Hered. dans les Maladies,' judging from the paper first published 



1840, p. 135. For Hunter, see Har- in the ' Baltimore Med. and Phys. 



lan's ' Med. Researches,' p. 530. Reg.' 1809, of which Mr. Sedgwick 



^^ ' L'Hered. Nat,,' torn. ii. p. 850. has been so kind as to send me a cop)'. 



^^ Sedgwick, ' Brit, and For, Med.- '^ Prosper Lucas, ' Hered. Nat. 



Chirurg. Review,' April, 1861, p, 485, torn. i. p. 400. 

 In some accounts the number of 



