444: DISEASES OF THE SKIN. 



which become distended by a collection of epithelial scales and glol> 

 ules of a fatty lustre. The tumors, which at first are scarcely larger 

 than a pea, and are covered by the normal skin, gradually enlarge, 

 while the skin becomes tense, red, and depressed in the middle, like a 

 runnel. New nodules develop in the vicinity of the first one, so that 

 finally a large area of the skin is often covered by these molluscous 

 tumors. This continuous progress, and the communication of the dis- 

 ease to other persons, the actual occurrence of which has been well 

 authenticated in several instances, indicate that it is of a contagious 

 character. The bearer of the contagion seems to be the fatty globules 

 above mentioned. 



CHAPTER I. 



DIFFUSE HYPERTROPHY OF THE PAPILLARY LAYER AND OF THE 

 EPIDERMIS ICHTHYOSIS. 



ETIOLOGY. It has been stated already that the exuberant forma- 

 tion of epidermis, which takes place in ichthyosis, is due to an abnor- 

 mal development of the papillary layer of the matrix of the epidermis. 

 Barensprung, of whose excellent work upon cutaneous diseases we 

 have made free use whenever the publications of this profound inves- 

 tigator have been available, makes a distinction between congenital 

 ichthyosis in its narrowest sense, where the child comes into the world 

 clad in a thick horny corselet, and the true ichthyosis. In the former 

 affection the child is born dead, or dies soon after birth, and it would 

 appear that the horny case which covers it must have formed at an 

 early period of intra-uterine life, probably through melting together of 

 the caseous varnish composed of cells of epidermis and cutaneous se- 

 cretion. It is always evident that the rigid horny coat, which is all 

 cracked into fragments, has become too small to cover the fully-grown 

 fcetus, and has crippled the development of its nose, lips, ears, fingers, 

 and toes. 



The papillary hypertrophy, which is the cause of the true ichthy- 

 osis, likewise appears to be an hereditary and congenital disease. The 

 fact that the malady nearly always remains undetected during the first 

 year of the child's life, is to be ascribed to the manner in which the 

 skin is cared for during that time. The family history of a patient 

 with ichthyosis often shows that other members of the family, brothers, 

 parents, or grandparents, or other relatives, have suffered from the 

 same disease. 



Besides the congenital true ichthyosis, which usually extends 

 over the entire surface of the body, there is a milder and acquired fora; 



