on the Reflex Function of the Spinal Marrow, 191 



duces a reflected affection of the facial and other nerves in 

 sneezing. But the great sensitive nerve of the anterior part 

 t)f the head and the face, the great portion of the trigeminus, 

 may excite the oculo-motor and facial through the medium of 

 the brain ; thus contraction of the iris takes place when cold 

 water is thrown into the nose, and from tickling in the nose 

 sneezing takes place, as well as the action of the facial nerve in 

 theexcitementofthe facial muscles which is connected with it. In 

 sliort, we see, that of the motor cerebral nerves, the part of the 

 oculo-motor nerve which goes to the ciliary ganglion and 

 thence to the iris, and the facial nerve, may most easily be ex- 

 cited by reflexion, and that the impressions either of sight, or 

 touch, or hearing maybe the exciting causes: therefore between 

 the origins of the optic, trigeminus, and auditory nerves, and 

 the points of origin of the motor nerves in the brain, there 

 must be a facility of conduction pre-established by primitive 

 formation. Those sensitive and motor nerves, whose mutual 

 action is effected through the brain and spinal marrow, pre- 

 sent a kind of balance with those central parts, one altering 

 the other, as the ascent of one scale induces the descent of the 

 other, or as the falling of a fluid in one leg of a bent tube pro- 

 duces the ascent in the other, till they are permanently at an 

 equilibrium. If a sensitive nerve is not usually in a state to 

 produce a reflected motion, yet on any violent impression on 

 sensation it becomes so, and the brain and spinal marrow then 

 reflect the currents or vibrations received from the sensitive 

 nerves, into those motor nerves, to which the conduction from 

 the sensitive fibres through the fibres of the brain and spinal 

 marrow is most easy. 



"Another very common path of conduction from the sensi- 

 tive to the motor nerves through the medium of the spinal 

 marrow and medulla oblongata, is that seen in the excitation of 

 the mucous membranes aiid the secondary affection of the re- 

 spiratory muscles in vomiting, evacuation of faeces, parturition, 

 the coughing, sneezing, &c. Next to the above-mentioned law, 

 that nerves of allied origins, or of not very remote origins, are 

 peculiarly prone to the phenomena of reflexion, the most fre- 

 quently acting law of the "Nervenstatik" is the reflexion now 

 mentioned. Therefore, i?i the medulla oblongata and spinal 

 7narro'w, between the sensitive nerves of the mucous membranes 

 (the trigeminus in the nose; the vagus in the trachea,- lungs, 

 pharynx, oesophagus, stomach ; the sympathetic in the intes- 

 tinal canal and uterus; branches of the sacral plexus and sym- 

 pathetic in the urinary bladder and rectum ;) and the motor 

 respiratory nerves (facial, accessory, and spinal nerves), there 

 must be pre-formed easy means (or a conduction; while, on 



