SYMPATHY. 455 



as it affects animal contractility or sensibility, tetanus from a 

 wound in the extremities being an instance of the former and 

 pain of the knee in hip disease an instance of the latter ; and as 

 it affects organic contractility or sensibility, of which palpitation 

 from disorder of the stomach is an example , states that sym- 

 pathy of animal contractility occurs only when the nerves con- 

 necting the affected muscles with the encephalon or spinal chord 

 are entire. When he divided them, the convulsions in the cor- 

 responding muscles ceased : and the iris ceases to contract when 

 the third pair is divided, though light glares on the retina. 



Neither, where sympathetic muscular action arises from a sens- 

 ation, will it occur, if the nerves communicating impressions from 

 the affected part to the sensible part of the nervous centre are 

 compressed or divided, or if the brain itself is unable to receive 

 the impression. If the optic nerve is divided, the sun's rays will 

 not excite contraction of the iris. Although the stomach in an 

 animal newly dead may be thrown into contraction by mecha- 

 nical irritation, no sympathetic action of the diaphragm and ab- 

 dominal muscles,' no vomiting, occurs 1 ; in perfect coma neither 

 sneezing nor contraction of the iris can be induced by applying 

 stimulants to the nostrils or letting the sun's rays into the eye. 

 . The sympathies of the organic functions are not all ascribable, 

 as many might imagine, to continuity of surface ; for, after di- 

 viding the O2sophagus of a dog, Bichat produced vomiting equally 

 as before, on irritating the fauces m , and Dr. Brachet sneezing on 

 irritating the nasal membrane after having divided the trachea. a 



Sympathy depends on the peculiarity of the impression as well 

 as upon the part. " When the sides or soles of the feet are 

 tickled," says Dr. Whytt, " the body is often thrown into convulsive 

 motions ; but nothing of this kind happens when those parts are 

 either inflamed or wounded : neither an acrid injection of a so- 

 lution of corrosive sublimate, nor the introduction of a catheter 

 into the urethra, occasions any alternate convulsive motions of the 



stance ; as vomiting from the pregnant state ; Where there is proximity of the 

 sympathising parts ; as tenesmus when a stone exists in the urinary bladder : 

 and Where, as most commonly, the sympathising parts are continuous ; as 

 itching of the nose and verge of the anus from worms in the intestine. Treatise 

 on the Blood, <%c. Introduction. 

 . J Dr. Whytt, On the Vital and Involuntary Motions. 

 m Anat. Generate, t. i. p. 192. ' 1. c. p. 298. 



