148 OF FOOD, AND THE DIGESTIVE PROCESS. 



viscid substances, whilst its presence is of great importance in enabling the 

 tongue to perform the rapid movements requisite for distinct articulation, as 

 is clearly indicated by the thick and almost unintelligible utterance of those 

 in whom from any cause the mouth and tongue have become dry and parched. 

 Lastly, there can be no doubt that it has a powerful chemical action upon 

 the farinaceous constituents of food, the influence being of a continuous 

 nature, and resembling the action of a ferment, so that a small proportion 

 of Ptyalin will convert a considerable, though, according to Paschutin, 1 not 

 an indefinite quantity of starch into sugar. In Mialhe's experiments, one 

 part of Ptyaliu was found to effect the conversion of 2000 parts of starch, 

 first into dextrin and then into grape sugar. If the starch be crude or raw 

 the time required is considerable, 2 amounting to two or three days even at 

 blood heat, but the rapidity with which it takes place under favorable circum- 

 stances is very great ; thus Viutschgau 3 found that if well boiled, thin starch 

 paste, which had been rendered blue by the addition of Iodine, were added 

 drop by drop to Saliva at a temperature of 98 or 99 F., the color instantly 

 disappeared ; and Dr. Dalton found traces of sugar in starch-paste which had 

 been kept in the mouth within 30 seconds. The temperature at which the 

 action is most intense is from 100.4 F. to 105.8 F.* This power is not 

 peculiar, however, to the Saliva ; for M. Bernard has shown that many 

 azotized substances in a state of incipient decomposition, exert a similar 

 agency : still it appears to be possessed by Ptyalin in a much greater degree 

 than any of these (save the pancreatic fluid, which resembles saliva in this 

 property), the transformation of starch under its influence commencing im- 

 mediately, and continuing energetically until it is entirely effected. The 

 activity of Ptyalin is destroyed by a boiling temperature. Its presence has 

 been ascertained in man in the saliva secreted by all the glands ; but in the 

 dog it is absent in the parotideau fluid, and it exists only in small quantities 

 in the secretion of the other salivary glands, which is in accordance with the 

 nature of the food of this animal. In man, the transforming process is cer- 

 tainly not checked on the passage of the food into the stomach, as it is in the 

 dog, which is partly owing to the larger proportion of Ptyaliu his saliva con- 

 tains, and partly to the acidity of the gastric juice being much less. It 

 would appear that the Saliva has little or no chemical action on either the 

 oleaginous or on the azotized constituents of the food, and its operation on 

 them, if it have any, must therefore be purely physical. 



105. The secretion of the saliva takes place remittingly under nervous in- 

 fluence, the conditions of which have been very carefully investigated by 

 Bernard, 5 Ludwig, 6 Eckhard, 7 Schiff, 8 v. Wittich, 9 and Bidder. 10 In the 

 dog, the submaxillary and sublingual glands are supplied by the Sympa- 

 thetic and by a nervous circle formed by the Glosso-pharyngeal and Fifth 

 as sensory nerves, and the facial as a nerve exciting secretion, the active 

 fibres of the latter passing into the chorda tympani nerve, and proceeding to 

 the submaxillary ganglion. The different action of the sympathetic fibres, 

 and of those coursing in the chorda tympani, when stimulated, is very curious, 

 effecting actually a change in the character of the Saliva secreted. If the 

 two glands above mentioned are cleanly dissected out, they may be seen at 



' Centralblatt, 1871, p. 372. 2 Schiff, Physiologic de la Digestion, 1867, p. 153. 



3 Atti del Institute) Veneto, t. iv, 18-^9. 



4 Pnscluitin, Centralblatt, 1870, p. 577. 



6 Lectures, Med. Times and Go/., vol. i, 1800, pp. 288-3G1. 



6 Lehrbuch dor Physiologic, Hand ii. 



7 Ik'itragc, J'xl. ii, p 2<>">; in, 18(12, p. 41 ; iv, 1807, Heft 2. 



8 Physiologic, 18")!, p. :->!)3. 9 Virchow's Archiv, Bd. xxvii and xxxix. 

 1 Reichert and Dubois-Reymorid's Archiv, I860, p. 339. 



