566 DIGESTION. 



ary principles. In an alkaline fluid, all three have the power of trans- 

 forming starch, and do not digest meat; whilst in an acid fluid they 

 dissolve meat, but do not act on starch. Hence, they think, it appears 

 easy to transform these fluids into each other, and to make for example 

 an artificial gastric juice from pancreatic fluid. The action of saliva, 

 however, is said to be less energetic, both on meat and starch, than the 

 pancreatic fluid. For the organic compound in the saliva, M. Mialhe 1 

 proposes for it the name animal diastase salivaire. It would seem, how- 

 ever, from the experiments of MM. Magendie 2 and Bernard, 3 that many 

 substances besides saliva, as pieces of the mucous membrane of the 

 mouth, bladder, rectum and other parts, various animal and vegetable 

 tissues, and even morbid products effect the transformation of starch into 

 sugar; but that the gastric fluid does not. The part of the saliva, 

 according to M. Bernard, which appears to be most active is that 

 secreted by the small glands and the mucous membrane of the mouth; 

 but it has been properly observed, by Messrs. Kirkes and Paget, 4 that 

 if the influence of saliva in aiding the digestion of farinaceous food be 

 admitted, we have yet to seek for the corresponding purpose served by 

 the saliva of the carnivora, which consume no such food; and on this 

 point we possess at present no information. 



It is probable, however, that the main action of saliva is to soften 

 the food; for when substances are well mixed with water, they are 

 retained in the mouth for a short time only ; and, consequently, in an 

 amylaceous solution there is no opportunity for change to be effected. 

 Experiments, instituted by M. Lassaigne, 5 by a committee of the 

 Institute, and by M. Bernard 6 show, that when the food is dry a con- 

 siderable admixture of saliva takes place, whilst if it be so softened, 

 that mastication is not needed, it absorbs scarcely any. In executing 

 these experiments, the aliment was weighed before giving it to the 

 animal; the esophagus was cut across; and the aliment, after having 

 been chewed and insalivated, was inserted through the wound in the 

 neck. The difference in weight indicated the quantity of saliva that 

 had been added to it. 



According to Professor Berard, 7 these experiments teach us : First. 

 That dry forage absorbs about four or five times its weight of saliva and 

 mucus. Secondly. That dry feculaceous articles (oats, starch and bar- 

 ley meal) absorb a little more than their weight. Thirdly. That green 

 forage (green leaves and stalks of barley) absorb a little less than half 

 their weight; and fourthly ; that moist feculaceous articles (starch and 

 bran) to which sufficient water has been added for the food to be swal- 

 lowed without previous mastication, do not sensibly absorb any. 



Both mastication and insalivation are of moment, in order that diges- 

 tion shall be accomplished in perfection; and, accordingly, they who 



1 Lancette Franaise, Avril, 1845; and Banking's Abstract, vol. i. Part, ii., Amer. edit., 

 p. 270, New York, 1846. 



2 Comptes Rendus, 1847, p. 117. 



3 Canstatt und Eisenmann, Jahresbericht uber die Fortschritte in der Biologic, im Jahre, 

 1847, s. 117. 



4 Manual of Physiology, Amer. edit., p. 162, Philad., 1849. 



5 Journal de Chimie Medicale, p. 472, Paris, 1845. ^ 



6 Archives Generates de Medecine, 4e serie, torn. xiii. p. 1. 



7 Cours de Physiologic, p. 721, Paris, 1848. 



