* " The system of the respiratory nerves maybe thrown into morbid action, 

 producing convulsive motions, by local stimuli in all parts which are pro- 

 vided with mucous membranes. Stimuli applied to the mucous membrane 

 of the nose, produce sneezing ; in the pharynx, oesophagus, stomach, or in- 

 testines they produce the concurrence of the respiratory motions, in vomiting; 

 while powerful stimuli in the rectum, urinary bladder, or uterus, produce a 

 concurrence of respiratory motions in the involuntary discharge of faeces or 

 urine, or the expulsion of the foetus. Stimuli of the mucous membrane of 

 the larynx, trachea, and lungs, nay, even a stimuhis exciting a tickling in 

 the Eustachian tube, produce cough. 



" All these involuntary motions, cough, vomiting, spasmodic involuntary 

 discharge of faeces, the forced passage of urine, are produced with the assis- 

 tance of the respiratory motions. The local stimulus here acts from the 

 inner membrane of the viscus, on the branches of the sympathetic ramifying 

 therein, and in the stomach, pharynx, trachea, and lungs, on the branches of 

 the vagus which they receive, or in the nose on the nasal branch of the tri- 

 geminus, and is reflected to the source of the respiratory motions in the me- 

 dulla oblongata and to the spinal marrow, from which proceed the groups of 

 respiratory motions that produce vomiting, cough, sneezing, &c. Stimuli 

 of the nasal branches of the trigeminus produce sneezing, even when se- 

 condary ; for instance, when the stimulus of the sun's light acts first on the 

 optic nerves, the latter act on the brain, and the brain causes a secondary 

 excitement of the nasal nerves and coincidently of the respiratory nerves. 

 I, like many other persons, sneeze as soon as I see bright sunlight. Sti- 

 mulus of the vagus alone in the larynx, trachea, and lungs excites cough, 

 that of the pharyngeal branches of the vagus and glossopharyngeal in the 

 pharynx, or of the vagus in the stomach, excites vomiting. We will now go 

 through the several groups of these sympathetic respiratory motions. 



" All the several respiratory motions may be produced in an isolated man- 

 ner, and sometimes are united in groups, such as do not regularly occur in 

 respiration. 



" The contraction of the diaphragm, united with the motions of respira- 

 tion, takes place, voluntarily or involuntarily, in the forcible expulsion of a 

 body from parts of the abdominal cavity ; e. g. voluntarily in the expulsion 

 of fceces and of urine, involuntarily in vomiting, parturition, involuntary ex- 

 pulsion of faeces after their too long retention, and in the involuntary dis- 

 charge of urine long retained. The pharynx, stomach, rectum, urinary blad- 

 der, and uterus, all stand by means of their nerves in such connexion with the 

 cerebral and spinal nerves, that a violent stimulus applied to any one of them, 

 excites contraction not merely in it, but also in the abdominal muscles and 

 diaphragm, to the expulsion of the irritating matter upwards or downwards. 

 This effect takes place by reflexion to the brain of the stimulus of the branches 

 of the vagus in the pharynx and stomach, — to the sympathetic system and 

 to the brain and spinal marrow, from the sympathetic twigs of the stomach, 

 — and by the reflexion to the spinal marrow of the stimulus of the partly 

 sympathetic and partly sacral nerves in the rectum, uterus, and urinary 

 bladder. In all these motions for the expulsion of a part upwards or down- 

 wards, the glottis is for a long time closed. 



" For the explanation of the production of vomiting, an observation of 

 mine is very instructive, viz. that if we open the cavity of the abdomen in 

 a rabbit, and having exposed the splanchnic nerve on the left side (near the 



