218 DIGESTIVE SYSTEM. 



this (Schiff) ; Cohnheim has attempted in vain to prove that 

 ptyaline is not an albuminoid substance. 1 



The other elements of the saliva are salts, identical with 

 those of the blood, and also sulphocyanide of potassium. 

 The existence of this salt, first discovered by Treviranus, has 

 since been the subject of much dispute: the reaction by 

 which it is distinguished (red color produced by salts of 

 iron) has been attributed to acetates ; but distillation of the 

 saliva proves that it contains no acetic acid. It was then 

 supposed that the sulphocyanide was the result of decomposi- 

 tion or was produced only in pathological cases (hydrophobia 

 in dogs) or under the influence of certain nervous or moral 

 conditions (Eberle). But closer investigation of the subject 

 by Longet, CEhl, Sertoii, and Schiflf has shown that sulpho- 

 cyanide is an element which is always present in human 

 saliva, though its use is not yet understood. 



The secretion of the saliva offers a good example of the 

 influence exercised by the innervation of the secretions. 

 This secretion indeed is not the result of irritation directly 

 produced by the food ; the large salivary glands are too remote 

 from the buccal mucous. A reflex phenomenon takes place 

 here. The peripheral impression produced by the food is 

 transmitted by a special nervous organ to a reflecting centre^ 

 whence it is communicated to another organ (centrifugal 

 nerve) which determines the secretion. This reflecting 

 centre is not, as was long supposed, situated in the ganglions 

 of the great sympathetic nerve: numerous experiments have 

 proved that it is in the spinal cord. 2 The centripetal nerves 

 beginning in the mucous membrane, go to the bulb: these are 

 essentially the branches of the trigeminus. This function is 

 best shown by experiments on the nerve fibre called the 

 lingual, which is a branch of the inferior maxillary; but the 

 glosso-pharyngeal and pneumo-gastric nerves also take part 

 in the centripetal conduction ; for excitations of the stomach 

 cause secretion of the saliva, and we know that vomiting is 



1 See E. Ritter, " Des Phenomenes Chimiques de la Digestion." 

 These de Concours, Strasbourg, 1SG6. 



2 Cl. Bernard believed that he had proved that the sub-maxil- 

 lary ganglion may serve as a centre of salivary secretion, and this 

 was generally considered a sufficient reason for asserting that 

 the ganglions of the great sympathetic nerve possess the property 

 of reflex centres; but this opinion can no longer be held in the 

 presence of Schrff's contradictory experiments. (See Schiff, 

 44 Lemons sur la Physiologie de la Digestion." Florence, 1836.) 



