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doubt that psoriasis not uncommonly occurs in several 

 members of a family, and that it may be transmitted for 

 several generations. Dr. McCall Anderson's view as to the 

 cause of this affection is that it is an inherited perverted 

 tendency of tissue formation, which tendency lies dormant 

 until called into activity by some exciting cause ; and it is 

 probably not due to a special blood condition, or dyscrasia, 

 or diathesis, but is due to a peculiar morbid tendency of 

 parts of the skin, which is obviously hereditary. In other 

 words, it is neither primarily nor altogether due to any 

 condition of the blood or nervous system, but its causation 

 materially consists in an inherited proclivity of cutaneous 

 tissue an idiosyncrasy in the structure of the skin itself. 

 Mr. Hutchinson explains the entire absence of psoriasis in 

 infancy and early childhood by suggesting that when the 

 structural idiosyncrasy is very strong, it may manifest itself 

 in a different form. Thus, he thinks it not improbable that 

 the ichthyosis of infants may be in this way the representative 

 of the psoriasis tendency in its intensest form. Psoriasis is, 

 therefore, markedly hereditary, persisting through many 

 generations, and will sometimes be found to undergo 

 apparent transmutation with other forms of skin disease, as 

 nummular eczema, lichen ruber, and pemphigus. 



Of all other skin diseases, none affords such direct proof 

 of its hereditary character as ichthyosis, which generally 

 occurs in several members of the same family, but frequently 

 omits a generation, or fails to descend in the direct line. 

 Hardy goes even so far as to assert that if other members of 

 the family are not found affected with ichthyosis, this disease 

 will certainly be found affecting some near friend of the 

 patient's. There are many instances on record where the 

 disease was transmitted from mother to son, and from father 



