44 PHYSIOLOGY. 



ternal surface of the lungs, but the patient has no distinct 

 feeling between this and the insular pain in the pleuritis 

 spuria. The same is true with regard to the pain of the 

 head, whether within the cranium or without ; only, finding it 

 affected by external pressure, we suppose it to be in the external 

 parts. And, in like manner, with regard to the abdominal region : 

 as there is here a succession of parts lying upon one another, 

 we cannot from the sensation say which is the place. Thus, a 

 pain in the pit of the stomach may arise from the stomach 

 itself, or from the adjacent biliary duct, from the liver, the 

 pancreas, &c. With respect to feelings referred to internal 

 parts, therefore, we can only form our judgments from the 

 affections of the functions accompanying them." 2. Sensations 

 are sometimes referred, not to the part upon which the impres- 

 sion is immediately made, but to a distant more sensible part, 

 to which a motion is propagated from the part impressed. 

 " This is a matter of much nicety, and shews the fallacy of the 

 general rule, that sensations are referred to the part on which 

 the impressions are made. It is sufficiently known, that from 

 impressions made upon one part, motions may be propagated 

 to other parts, as in the case of a very acute sound, such as 

 that produced by a file, or by a bit of cork rubbed upon the 

 table, giving an uneasy sensation in the teeth ; and in the case of 

 the stone in the bladder, which can only act upon the neck of 

 the bladder, but the pain from which we perceive only at the 

 point of the urethra. In like manner, a pain arising from a 

 stone in the pelvis of the kidneys, or in the beginning of the 

 ureters, propagates a motion along the course of the urethra 

 from the neck of the bladder, and is exquisitely felt only at the 

 orifice of the urethra. With regard to other instances there 

 may be more doubt, but I will mention them : When a rheu- 

 matic affection attacks the hip-joint, a feeling is commonly pro- 

 pagated downwards to the knee, where it shoots out in violent 

 pain; the same feeling goes still downwards, and then a 

 sharp pain is felt in the ankle. In some cases it may be a 

 question whether or not the rheumatic affection is in the knee 

 as well as in the hip-joint, or in the ankle as well as in the other 

 two parts. But in many of these cases we have reason to be- 

 lieve that the rheumatic affection is confined to the hip-joint 



