REFERRED PAIN 193 



difficulties. Muscles and fasciae, though not so acutely 

 sensitive as the skin, may be the site of painful sensations and, 

 therefore, abdominal pain felt on a deeper level than the 

 skin is not necessarily experienced in an abdominal viscus. 

 Mackenzie has come to the conclusion that the viscera them- 

 selves are insensitive to painful stimuli and that they can 

 only give rise to pain through a viscero-sensory reflex. He 

 has been able to adduce a large mass of evidence in support 

 of this view, but it is opposed by evidence which is difficult 

 to controvert. 



The investigation of the question is necessarily carried out, 

 for the most part, on patients who are quite devoid of 

 anatomical knowledge, and the difficulty they experience in 

 localising abdominal pains is increased thereby. This 

 difficulty is caused by the presence of the abdominal walls, 

 which conceal the viscera, and by the absence in the viscera 

 of any sense corresponding to the muscle and joint sense in 

 the limbs. A healthy person is not conscious of his viscera, 

 as the nervous mechanism which controls them is, for the 

 most part, entirely automatic. On the other hand, a healthy 

 person is always conscious of the position of those parts of the 

 body which are supplied by cerebro-spinal nerves. If one 

 attempts to localise the exact position of a painful area in the 

 hand through a piece of wood or some other solid object, it 

 is found that such localisation, though aided by muscle and 

 joint sense, is by no means accurate. In the light of this 

 experiment, one can appreciate the difficulty of localising an 

 abdominal pain, if one assumes that the pain is felt only in 

 the viscus and that the sensibility of the abdominal wall is 

 not affected. Consequently, when a painful area indicated 

 by a patient does not exactly correspond in size or position 

 to the viscus in which it is supposed to originate, it does 

 not necessarily follow that the pain is not felt in the viscus 

 itself. 



Further, many medical men, who have suffered from colitis 

 or some other painful condition of the large intestine, state 

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