SYMPATHY. 453 



yet the irritation of this, independently of distension, excites the ac- 

 tion of the muscular tissue. In disease these sympathies are some- 

 times more striking ; because there may be an undue excitement 

 of the part influencing, or undue excitability of the part influ- 

 enced. An exquisitelysensible growth at the end of the rectum may 

 produce tenesmus of the expelling muscles. On the other hand, 

 in morbid excitability of the intestines, although the stomach be per- 

 fectly healthy, the ingurgitation of warm fluid into it will often cause 

 immediate defecation ; in neuralgia, at a distance from the sto- 

 mach, oppositely, I have seen an instant aggravation of pain when 

 any thing was swallowed ; and I have attended two cases of violent 

 cough in young men from the slightest touch of one half of the 

 chest , though this was not in the least tender ; indeed we have the 

 skin exquisitely tender in some cases of hysteria, and when it is in- 

 flamed, without such effect. Sometimes natural sympathy may lan- 

 guish from the want of excitement in the influencing part or of 

 excitability in the influenced. The iris will not contract by light 

 if the retina becomes insensible ; and, on the other hand, if the 

 nerves of the iris are paralysed, the stimulation of the retina by 

 light will fail to excite the iris to contraction. 



Sympathies occur in disease between parts which are not 

 observed to sympathise at all in health ; and the disease may be in 

 the affecting or affected part. When the liver is inflamed, the 

 right shoulder often aches ; when the hip joint is diseased, the 

 knee is often the seat of severe pain ; on the other hand, pain 

 in an extremity often increases the very instant that stimulating 

 articles are swallowed which in health scarcely caused a glow 

 even in the stomach, and which still do no more than this in the 

 stomach while they aggravate the pain. In disease new sym- 

 pathies occur between parts which naturally sympathise, as when 

 constipation of the intestines produces vomiting ; and the breasts 



1 I presume that, as the sensibility of both halves of the surface was the same, 

 the reason of such effects from touching the one only was, that the morbid ex- 

 citability existed in that half only of the expiratory part of the spinal chord with 

 which the nerves of sensation of that side were connected, and with which the 

 expiratory portion of the other side sympathised. In hydrophobia, a slight blast 

 of air, or the settling of a fly upon the surface, causes the inspiratory muscles to 

 act suddenly and violently, though the skin is not tender to the touch. Yet I will 

 not adduce this to illustrate the second cause of morbid sympathy, because a 

 strong flash of light has the same effect ; and light/noise, and the application of 

 cold to the surface, or any slight and sudden eause of sensation, are very un - 

 pleasant, and show a morbid sensibility of all the external senses, 



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