274 ra GICA L APPLIED ANA TO MY. [Chap, x v i . 



important to note that they supply not only the 

 abdominal integument, but also the muscles of the 

 belly, viz., the rectus, the two oblique muscles, and 

 the transversalis. This association is of great prac- 

 tical importance. If a cold hand be suddenly placed 

 upon the belly the muscles at once contract and the 

 abdomen is instinctively rendered rigid. The safety 

 of the viscera, so far as at least protection from 

 contusions is concerned, depends upon the readiness 

 with which the muscles can contract at the first 

 indication of danger. As has been already stated, the 

 viscera have a very efficient protection against the 

 effects of blows when the belly muscles are in a state 

 of rigid contraction. The sensitive skin acts the part 

 of a sentinel, and the intimate association of the surface 

 nerves with the muscular nerves allows the warnings 

 of this sentinel to be readily given and immediately 

 acted upon. If the skin and the muscles had each 

 an independent nerve-supply, a longer interval would 

 elapse between the warning to the skin and the 

 muscular contraction than occurs when those two 

 parts are both supplied by the same nerves. The 

 rigidity of the muscles in certain painful affections of 

 the skin over the abdomen is often very conspicuous. 

 I might instance the case of a man with a burn over the 

 belly. While the burn is protected by the dressings 

 the abdominal muscles are lax and the parietes move 

 with the respiratory act. The moment the dressings 

 are removed, the surface becoming painful, the 

 muscles at once contract and the belly becomes 

 rigid. It will be noticed that seven of the abdominal 

 nerves supply intercostal muscles, and are thus 

 intimately associated with the movements of respira- 

 tion. The abdominal muscles are of course concerned 

 in the same movements. These associations are illus- 

 trated when cold water is suddenly dashed upon the 

 belly. The subject of such experiment at once 



