388 INNERVATION. [CHAP. XII. 



kind. These motions or sensations are produced in, as it were, an 

 indirect or circuitous manner, or one different from that in which 

 they are ordinarily excited. 



Thus a stimulus to the olfactory membrane causes a peculiar 

 affection of the sense of smell, and thus occasions that depression of 

 the heart's action from which results a state of syncope. Or, 

 another affection of the same sense causes a suddenly increased 

 action of the salivary glands. 



If we analyse any one of these examples of sympathetic actions, it 

 will appear that three circumstances are to be noticed in the produc- 

 tion of the phenomena : 1st, the primary exciting cause, which may 

 be an object presented to the mind through one of the organs of 

 sense, or causing an impression upon any sensitive nerve, and there- 

 fore upon some part of the centre of sensation ; 2ndly, the part 

 affected directly by this primary stimulus ; and, 3rdly, the action or 

 sensation resulting from the affection of this part. 



Many other sensations or motions may be enumerated besides 

 those above referred to, whether occurring in health or in disease ; 

 and we shall give examples of these before we discuss this subject 

 further. 



The examples of sympathetic sensations which may be adduced 

 are chiefly of the morbid kind. Pain is felt at a certain part, in 

 consequence of an irritation in another part distant from it, and ap- 

 parently altogether unconnected with it. One of the most familiar of 

 these is pain in the knee from disease of the hip-joint. So marked 

 in some instances is the pain in the knee, and so much has it absorbed 

 the patient's attention, that the real seat of the disease has been 

 overlooked, and the remedies been applied exclusively to the knee. 

 Pain in the right shoulder from disease of the liver is a sympathetic 

 sensation of similar kind; and sometimes the hepatic irritation causes 

 pain over a more extensive surface. Whytt mentions, that, in two 

 cases of suppuration of the liver, he had seen the patients " affected 

 with a numbness and debility of the right arm, thigh, and leg/' 

 The peculiar sensations felt in the teeth from a noise which grates 

 upon the ears, is sympathetic of the irritation of the auditory nerve. 

 Practitioners are well aware haw many morbid sensations in parts 

 remote from the intestinal canal may be cured by the removal of 

 scybala or other accumulations from it. Painful affections of the 

 nerves of the face, and of other parts, are often due to a cause of 

 this kind. The irritation of a stone in the bladder gives rise to 

 pains in the thighs, or to itching at the end of the penis ; and 

 uterine irritation, whether from disease or from the enlargement of 



