ACTION OF THE GASTRIC JUICE IN DIGESTION. 243 



manner, many physiologists, while professing to assign definite and distinct properties to 

 each, thus investing the function of digestion with the attraction of simplicity, have 

 necessarily ignored or distorted facts and have assumed a completeness for the sum of 

 our information on this subject, which does not exist. 



When the acts which take place in the mouth are properly performed, the following 

 alimentary substances, comminuted by the action of the teeth and thoroughly insalivated, 

 are taken into the stomach : muscular tissue, containing the muscular substance envel- 

 oped in its sarcolemma, blood-vessels, nerves, white fibrous tissue holding the muscular 

 fibres together, interstitial fat, and a small quantity of albumen, fibrin, and corpuscles 

 from the blood, all combined with a considerable quantity of inorganic saline matters; 

 albumen, sometimes unchanged, but generally in a more or less perfectly coagulated con- 

 dition; fatty matter, sometimes in the form of oil and sometimes enclosed in vesicles, 

 constituting adipose tissue ; gelatine and animal matters in a liquid form extracted from 

 meats, as in soups ; caseine, in its liquid form united with butter and salts in milk, and 

 coagulated in connection with various other principles in cheese ; vegetable nitrogenized 

 principles, of which gluten may be taken as the type ; vegetable fats and oils ; saccharine 

 principles, both from the animal and the vegetable kingdom, but chiefly from vegeta- 

 bles ; the different varieties of amylaceous principles ; and, finally, organic acids and salts, 

 derived chiefly from vegetables. These principles, particularly those from the vegetable 

 kingdom, are united with more or less innutritions matter, such as cellulose. They are 

 also seasoned with aromatic principles, condiments, etc., which are not directly used in 

 nutrition. 



The various articles coming under the head of drinks are taken without any consider- 

 able admixture with the saliva. They embrace water, the various nutritious or stimulant 

 infusions (including alcoholic beverages), with a small proportion of inorganic salts in 

 solution. 



All the articles enumerated above are more or less modified in the stomach ; and the 

 action of the gastric juice upon them will now be taken up in detail. 



Action of the Gastric Juice upon Meats. There are three ways in which the action 

 of the gastric juice upon the various articles of food may be studied. One is to subject 

 them to the action of the pure fluid taken from the stomach, as was done by Beaumont, in 

 the human subject, and by Blondlot and others, in experiments upon the inferior animals ; 

 another is to make use of properly-prepared acidulated infusions of the mucous membrane 

 of the stomach, which have been shown to have sensibly the same properties as the gastric 

 juice, differing only in activity ; and another is to examine from time to time the contents 

 of the stomach after food has been taken. By all of these methods of study, it has been 

 shown that the digestion of meat in the stomach is far from being complete. The parts of 

 the muscular structure most easily attacked are the fibrous tissue which holds the muscular 

 fibres together, with the sarcolemma, or sheath of the fibres themselves. If the gastric 

 juice of the dog be placed in a vessel with finely-chopped lean meat and be kept in contact 

 with it for a number of hours at from 80 to 100 Fahr., agitating the vessel occasionally 

 so as to subject, as far as possible, every particle of the meat to its action, the filtered fluid 

 will be found increased in density, its acidity diminished, and presenting all the evidences 

 of having dissolved a considerable portion of the tissue. There always, however, will 

 remain a certain portion which has not been dissolved. Its constitution is nevertheless 

 materially changed ; for it no longer possesses the ordinary character of muscular tissue, 

 but easily breaks down between the fingers into a pultaceous mass. On subjecting this 

 residue to microscopical examination, it is found not to contain any of the white inelastic 

 fibres; and the fibres of muscular tissue, although presenting the well-marked and char- 

 acteristic striae, are broken into short pieces and possess very little tenacity. It is evi- 

 dently only the muscular substance which remains; the connective tissue and the sarco- 

 lemma having been dissolved. These facts we have repeatedly noted, and, even on adding 



