220 



neurotic, and pigmentary diseases ; and disorders of the 

 hair and glands and their appendages. With the exception 

 of the first viz., the eruptions of the acute specific diseases 

 which I have already discussed and, perhaps, some of 

 the parasitic diseases of the hair, there is not one of these 

 forms which does not come, more or less, under the influence 

 of heredity. With regard to these two exceptions, heredity, 

 as I have elsewhere stated, shows its potency, as in the whole 

 range of organic life, for it develops, sustains, and perpetu- 

 ates the specific characters of the germs in the one, as it 

 develops, sustains, and perpetuates the specific characters of 

 the parasites in the other. How else could they be handed 

 down unaltered in their specific characters, from generation 

 to generation, except in accordance with the all-pervading 

 universal law, roughly estimated by Lamarck viz., " Like 

 begets like "; and " Each after his kind," as the Mosaic 

 record has it ? As I have said repeatedly before, there is 

 no escaping the law of heredity, for it is as necessary for our 

 development and perpetuation as the act of generation, or 

 the air we breathe ! 



The causes of skin diseases may be thus stated : 



(a) Internal, or those which act from within the system 

 upon the skin. 



(b) An innate disposition in the skin tissues themselves to 

 take on a diseased action. 



(c) External, or those which act from without the system 

 upon the skin. (Fox.) 



I am here only concerned with the two former, in which 

 many of the causes are hereditary ; but as similar diseases 

 may arise from a combination of both of these causes, it 

 may be expedient to consider them together, or rather to 

 consider these morbid conditions of the skin in the causation 



