AUTONOMIC NERVOUS SYSTEM 477 



be opened under local or general anaesthesia, subsequent cutting and 

 suturing of the gut may be conducted without any anaesthetic and with- 

 out causing any pain to the patient. On the other hand, impulses may 

 arise in the afferent nerve-endings of the viscera, as a result of disease or 

 certain forms of stimulation, e.g. stretching or compression, which may 

 reach consciousness and give rise to the sensation of pain. This pain is 

 not localised in the viscera, but is referred to certain parts of the surface 

 of the body. When the afferent autonomic fibres of a nerve are the seat of 

 pain, the primary referred pain is in the area of the cutaneous somatic fibres 

 of the nerve. It has been shown by Mackenzie and by Head that visceral 

 disease may cause hyper-sensitivity of the corresponding areas of the skin, 

 and a method has been elaborated by these observers for utilising this 

 referred pain or skin tenderness as a means of localising the site of the 

 disease. 



