viii] in the Eighteenth Century. 219 



must, we might fancy, have come upon evidences of acidity 

 so distinct that he could not overlook it. Possibly even he, 

 accurate and unbiassed observer as he certainly was, may have 

 been misled by preconceived opinion; when he came upon 

 acidity he regarded it as something abnormal. 



Be it as it may, by Spallanzani's labours, the fact of 

 the solvent power of gastric juice as a power which was sui 

 generis, the solution effected by which was not the solution of 

 putrefaction, or of any other known form of fermentation such 

 as might occur under various circumstances, whether within 

 or outside the stomach, became an established fact, a definite 

 addition, never afterwards taken away to our knowledge of 

 digestion. 



I ought to add that in an Inaugural Dissertation which 

 appeared in the same year as Spallanzani's first memoir, namely 

 in 1777, Stevens of Edinburgh, adopting Reaumur's methods, 

 had arrived at results similar to those of the French and 

 Italian inquirers. Taking advantage " of a man of weak under- 

 " standing who gained a miserable livelihood by swallowing 

 " stones for the amusement of the common people," Stevens 

 made him swallow silver perforated spheres containing pieces 

 of food, animal and vegetable, raw and cooked and including 

 bone ; he found on examining the spheres, when after some 

 forty-eight hours they were voided, that the food was for the 

 most part dissolved ; whole grains however of wheat, peas, &c. 

 were but little changed. He continued his experiments on 

 dogs, making them swallow similar spheres, killing them after 

 a variable number of hours and opening their stomachs. He 

 repeated the experiments on sheep and oxen, and found that 

 while these digested readily vegetables, hay and herbs, their 

 stomachs had little action on animal food. He then obtained 

 'pure gastric fluid' from the stomach of a dog killed after a 

 fast of sixteen hours, and found that this fluid at a temperature 

 of 102 — 104° Fahr. readily dissolved cooked meat, without any 

 putrefaction and without any development of air bubbles. He 

 thus came with Spallanzani to the conclusion that digestion " is 

 " not the effect of heat, trituration, putrefaction or fermentation 

 " alone, but of a powerful solvent secreted by the coats of the 



