CHAP. II.] RESEARCHES ON DIGESTION DURING THE 18TH CENTURY. 69 



tion, but with which he was utiable to effect digestion outside of the 

 body. 



Reaumur, whilst convincing himself that in certain animals a 

 chemical solvent plays an important part in the work of the stomach, 

 was perplexed by the fact that vegetable food escaped the influence 

 of the gastric juice, and was thus prevented from establishing that the 

 essential of gastric digestion in all animals is the chemical action of 

 the gastric juice upon certain of the constituents of food. 



me re- The discoveries of Reaumur constituted an important 



searches of step in the discovery of the nature and processes of the 

 Stevens. gastric juice, and the subject was further elucidated by 



Dr Stevens, who in 1777 presented an Inaugural Thesis to the Univer- 

 sity of Edinburgh, entitled, 'De alimentorum concoctione.' He 

 availed himself of the presence in Edinburgh of a Hungarian who was 

 in the habit of swallowing stones and regurgitating them, a practice 

 which he pursued as a means of gain by public exhibition. Stevens 

 caused this man to swallow little silver balls perforated like a sieve, 

 constructed so as to be filled with food and then closed by screwing. 

 Dr Stevens found that the contained aliment was dissolved and some- 

 times completely disappeared, although protected from the influence 

 of trituration. By constructing a silver ball with a median partition, 

 the one half being more thickly studded with holes than the other, 

 and filling both with food, he found that it was most readily dissolved 

 in that division which contained most apertures. Additionally, 

 Stevens obtained the gastric juice from the stomach of a dog, and he 

 found that a piece of meat was digested by it outside of the stomach 

 in eight hours, provided it were placed in a vessel exposed to 

 warmth 1 . 



Spaiianzani ^ n ^ e ver y 7 ear i n which Stevens presented his 



thesis to the University of Edinburgh, the eminent 

 Italian naturalist Spaiianzani commenced his splendid investigations 

 on digestion. These investigations 2 , extending and corroborating 

 those of Reaumur and Stevens, shewed conclusively that gastric juice 

 was capable of effecting the same transformations when removed from 

 the body, if the conditions for its activity were favourable, as in the 

 stomach itself. He drew full attention to the antiseptic action of the 

 gastric juice, and insisted that the process by which food is digested 

 in the stomach is not akin to the ' alcoholic, acid and putrefactive 

 fermentations.' Without knowing the cause of the acidity of the 

 gastric juice, he yet recognised it, and asserted that the acid reaction 

 ceases when digestion is completed. 



1 Stevens, De Alimentorum concoctione, Edin., 1777. 



2 Spaiianzani, Experiences sur la Digestion de VHomme et de differentes especes 

 d'Animaux...Avec des conside rations... par Jean Senebier, Ministre de 1'Evangile, Biblio- 

 the'caire de la R^publique de Geneve. A Geneve, 1783. 



