282 SPECIAL PHYSIOLOGY. 



ness, for an animal will suck an object placed between its lips, or 

 swallow a mass of food placed on the back of the tongue, or close the 

 eyelids, if these be irritated, even though the functions of the brain be 

 suspended or destroyed. Persons in a profound state of comatose un- 

 consciousness and insensibility, from the effects of concussion of the 

 brain, or of chloroform or opium, will perform the same acts, and so 

 too will acephalous monsters. It has also been shown that the con- 

 tractile movements of the pupil, produced by the action of light, and 

 intended for protective purposes for the retina, and which are ordina- 

 rily accompanied by the special sensation of light, will occur in cases 

 of amaurosis, a disease characterized by alteration and consequent in- 

 sensibility of the retina, and in which there is absolute blindness. A 

 strong light also sometimes causes sneezing, by a reflex action through 

 the optic nerve, the cerebro-spinal centres, and the nerves which gov- 

 ern the respiratory movements ; this movement is automatic and sensori- 

 motor, for it is accompanied by pain. 



Furthermore, the medulla oblongata is, in some way, concerned in 

 the special senses of hearing and taste, containing, as it does, the deep 

 origins of the portio mollis of the seventh pair or auditory nerve, of 

 the glosso-pharyngeal nerve, and of the gustatory fibres of the fifth 

 pair. Its gray matter either constitutes the special centres of the 

 auditory and gustatory senses, the effects upon which are afterwards 

 transmitted to the common sensorium in the cerebrum ; or it serves as 

 an essential, but non-sensitive conducting path of the effects of sonor- 

 ous vibrations or of gustatory impressions, in their way upwards to the 

 cerebrum. 



It has been supposed that the gray matter of the olivary bodies, 

 with which the roots of the hypoglossal nerves are said to be connected, 

 has some special office in the government of the tongue and adjoining 

 parts, in the motions necessary to speech (Schroeder Van der Kolk); 

 but this view has not yet received the general sanction of physiolo- 

 gists. 



The formation of sugar in the liver is increased, by puncture, even 

 on one side, of the back of the medulla oblongata (Bernard), to such 

 a degree, that the urine becomes saccharine. Whether this is indi- 

 rectly owing to an interference with the respiration, or to some action 

 on the secreting power of the liver itself, is not known. 



Functions of the Pons Varolii, Cerebral Peduncles, and the gray 

 masses at the base of the Cerebrum, viz., the Corpora Striata, Optic 

 Thalami, Corpora Quadrigemina, Corpora G-eniculata, Pineal, and 

 Pituitary Bodies. 



In the first place, setting aside the transverse fibres of the pons, 

 which form the middle peduncles of the cerebellum, and also leaving 

 out of consideration the superior and inferior peduncles of that organ, 

 the latter being the continuation upwards of the restiform bodies, we 

 may regard the longitudinal fibres and the gray matter of the pons 

 and cerebral peduncles, as physiological extensions upwards, upon an 

 amplified scale, of the white and gray elements of the spinal cord and 



