EXTRACT XXXIX. 



ON URTICARIA. 



URTICARIA, or nettle rash, is an affection with which both 

 the laity and the profession are so very familiar that it has 

 perhaps thus escaped the scientific attention to which its 

 intrinsic nature otherwise entitles it. 



In intrinsic nature it is a neurosis, or, strictly speaking,, 

 a peripheral cerebro-spinal lymph disturbance, in which 

 that lymph, from local accumulation in certain nerve 

 terminal arborisations, it may be, associated with toxis, 

 distends those terminal textures and modifies their innerva- 

 tion, sometimes locally and sometimes generally, but always 

 in accordance with nerve terminal distribution raising the 

 super-imposed cuticle, and producing a sensation of 

 itching, tingling, and sensory distress often altogether 

 disproportionate to the visible and tangible local changes. 



It generally ensues from dietetic errors, and delivers its 

 attacks without previous warnings, these manifesting 

 themselves, "like bolts from the blue," in pale or more 

 or less tinted patches or areas conforming to afferent nerve 

 terminal distribution. 



The rapidity with which these cutaneous invasions 

 frequently ensue, after the exciting cause has been at work, 

 renders it probable that that exciting cause is of a subtle 

 toxic character, as rapid in the production of its effects as, 

 for instance, prussic acid and kindred toxic agents, and 

 operating along chemico-physiological lines determined by 

 the prevailing affinities between the toxic agent on the 

 one hand and the physiological tissue elements on the 

 other. Thus in urticaria arising from partaking of such 



