5't Prof. Miiller and Dr. M. Hall 



of the reflected motions after perceptions, from observations 

 which will be here further detailed. It is remarkable that 



inner side of the renal capsule) tear it with a needle, contraction of the 

 abdominal muscles often takes place. I have not seen this in the dog. 



** In cough, the stimulus of the vagus, in the larynx, trachea, and lungs is 

 propagated to the medulla oblongata. The medulla oblongata thereupon 

 excites contraction of the glottis, with spasmodic expiratory motions of the 

 thoracic and abdominal muscles, by which at each expiratory action, the 

 j)reviously closed glottis is somewhat opened and a loud tone produced. 

 The diaphragm has nothing to do with the cough, except that sometimes a 

 deep inspiration is made before coughing. According to Krimer^ and Bra- 

 chet, after division of the vagus on both sides of the neck of an animal, 

 cough can no longer be excited by violent stimuli of the internal surface of 

 the trachea. It certainly, however, may, according to Krimer, after division 

 of the sympathetic nerve in the neck. 



" We have the power of closing the entrance into the larynx, not merely 

 by the closure of the glottis, but even in the fauces from the nasal and oral 

 canals. Dzondi discovered that this takes place by the approximation of the 

 posterior arches of the palate, which lie almost hke two curtains approach- 

 ing each other from the sides, and by the apposition of the posterior part of the 

 tongue against this inclined plane. This motion always precedes sneezing. 



" Sneezing is a violent sudden contraction of the expiratory muscles, after 

 the air-passages anteriorly have been previously closed. This closure changes 

 at the momentof the violent expiration into a sudden opening of the oral and 

 nasal canals together, or of the latter alone. Sneezing has nothing whatever 

 to do with the diaphragm, which so many ancient and modern authors have 

 supposed to take a part in it. The widely spreading nervous sympathies 

 appear quite unnecessary in the explanation of sneezing. In the false suppo- 

 sition that sneezing is effected by the diaphragm, it was thought that the 

 stimulus of the nasal nerves was propagated to the deep twig of the Vidian, 

 and to the sympathetic, and from thence to the cervical and the phrenic 

 nerves. Even Arnold still speaks of this. Now as the expirat'ory muscles 

 (with previous closure of the mouth and nose) produce the act of sneezing, 

 and not the diaphragm, the simplest view is to regard the medulla oblongata 

 itself as the medium between the nasal branches of the trigeminus, the ex- 

 piratory muscles, and the muscles of the velum palati, after the analogy 

 of the sympathetic motion of the iris by the stimulus of light. For in this 

 case, as may be clearly shown, the stimulus of light acts neither imme- 

 diately on the ciliary nerves, nor from the retina to the ciliary nerves. 

 Tlie arteria centralis is indeed, according to Tiedemann's discovery, accom- 

 panied by a fine twig from the ciliary ganglion. But this twig is distributed 

 on the arteria centralis retinae, and is in no proved connexion with the re- 

 tina. In complete paralysis of the retina, light in general no longer pro- 

 duces contraction of the iris, though still through the healthy eye it does 

 produce a contraction of the iris of the diseased one. (There are however 

 exceptions to this rule, which Tiedemannhas collected in his Zeitschriftfur 

 Physiologie.) The motion of the iris therefore probably results from a re- 

 flexion of the stimulus of the retina to the brain, from the brain back to the 

 oculo-motor nerve, and the ciliary ganglion. The sympathies of a great 

 part of the nerves with a local stimulus through the medium of the brain 

 and spinal marrow, are very well shown in the phaenomena following the 

 narcotization of an animal, in which a slight touch on the skin produces ge- 

 neral tetanic spasms." — pp. 333 — 335. 



* Untersuchungen uber den Husten. 



