32 SECEETION. 



The motor nerve of the parotid is derived from the auri- 

 culo-temporal branch of the submaxillary division of the 

 fifth pair ; and the nerve of the sublingual, from the 

 lingual branch of the fifth. He found, however, that 

 neither the. parotid nor the sublingual was so easily ex- 

 cited to secretion by galvanization of the nerves as the 

 submaxillary. With regard to other glands, the condi- 

 tions for experimentation are so difficult, and some of them, 

 as the pancreas, are so sensitive to irritation, that it is impos- 

 sible to repeat on them the experiments made upon the sali- 

 vary glands. Enough is known, however, of the nervous 

 influences which modify secretion, to admit of the inference 

 that all the glands are possessed of nerves through which 

 reflex phenomena, affecting their secretions, take place. It 

 is the motor, or functional nerve of the gland through which 

 the reflex action takes place ; the influence of the sympa- 

 thetic being constant, and the same as in other parts where 

 it is distributed to blood-vessels. 



As reflex phenomena involve the action of a nervous 

 centre, it becomes an interesting question to determine 

 whether any particular parts of the central nervous system 

 preside over the various secretions. ' We must refer again to 

 the experiments of Bernard for an elucidation of this ques- 

 tion. If a puncture be made in the space included between 

 the origin of the pneumogastrics and the auditory nerves in 

 the floor of the fourth ventricle, there is an increase in the 

 discharge of urine, and an excretion of sugar, from an ex- 

 aggeration in the sugar-producing function of the liver. 

 Irritation applied a little higher, toward the pons varolii, just 

 posterior to the origin of the fifth pair of nerves, is followed 

 by a great increase in the activity of the salivary secretion. 1 



1 BERNARD, Lemons sur la physiologic et la pathologic du systeme nervcux, Paris, 

 1858, tome i., pp. 898-399. 



This operation is easily performed upon the rabbit, by passing an instrument 

 directly through the occipital bone, entering just behind the protuberance, and 

 through the cerebellum to the medulla oblongata. These experiments will be 

 more fully described in connection with the nervous system. 



