DISEASES OF THE SKIN. 



By James Law, F. R. C. S. V. S., 

 Professor of Veterinary Science, etc., Cornell University. 



[Revised in 1903 by the author.] 



As we find them described in systematic works, the diseases of the 

 skin are very numerous and complex, which may be largely accounted 

 for by the fact that the cutaneous covering is exposed to view at all 

 points, so that shades of dilference in inflammator}' and other diseased 

 processes are easily seen and distinguished from one another. In the 

 horse the hairy covering serves to some extent to mask the sj'mptoms, 

 and hence the nonprofessional man is tempted to apply the terra 

 "mange" to all alike, and it is only a step further to appl}^ the same 

 treatment to all these widely different disorders. Yet CA^en in the 

 hair}^ quadruped the distinction can be made in a way which can not 

 be done in disorders of that counterpart and prolongation of the skin — 

 the mucous membrane, which lines the air passages, the digestive 

 organs, the urinarj'- and generative apparatus. Diseased processes, 

 therefore, which in these organs it might be difficult or impossible to 

 distinguish from one another, can usually be separated and recognized 

 when appearing in the skin. 



Nor is this differentiation unimportant. The cutaneous covering 

 presents such an extensive surface for the secretion of cuticular scales, 

 hairs, horn, sebaceous matter, sweat, and other excretory matters, that 

 any extensive disorder in its functions may lead to serious internal 

 disease and death. Again, the intimate nervous sympath3^ of different 

 points of the skin with particular internal organs renders certain skin 

 disorders causative of internal disease and cei'tain internal diseases 

 causative of affections of the skin. The mere painting of the skin 

 with an impermeable coating of glue is speedil}'^ fatal; a cold draft 

 striking on the chest causes inflammation of the lungs or pleura; a 

 skin eruption speedily follows certain disorders of the stomach, the 

 liver, the kidneys, or even the lungs; simple burns of the skin cause 

 inflammations of internal organs, and inflammations of such organs 

 cause in their turn eruptions on the skin. The relations — nervous, 

 secretor}^, and absorptive — between the skin and internal organs are 

 most extensive and varied, and therefore a visible disorder in the skin 

 may point at once and specificall}^ to a particular fault in diet, to an 



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