22 SPALLANZANI 



or bone which proved trituration only a preparation for solution, and 

 that it was no further a part of the digestive process. 



He found that the gastric juice dissolved the food of animals into 

 a pultaceous mass or chyme. He observed that heat favored solution 

 and that in warm-blooded animals certain high temperature was 

 necessary for the chymification of foods. In Spallanzani's time putri- 

 faction was considered a form of fermentation. "There are three 

 kinds of fermentation, the vinous, the acetous, and the putrid." The 

 action of gastric juice was not putrid; in fact, it tended to arrest put- 

 refaction. Spallanzani was inclined to believe that the action of the 

 gastric juice was neither vinous nor acetous. Regarding the reaction 

 of gastric juice his conclusion was that it was neutral. He believed 

 that the acidity was due to an abnormality of the stomach contents, 

 inasmuch as the regurgitation of sour material from the stomach oc- 

 curred only when something had gone wrong. Spallanzani's failure to 

 t recognize the acidity of the gastric juice limited his further investiga- 

 tions. He could only conclude that the action of the gastric juice was 

 not fermentation, as fermentation was understood at the time. 



It is interesting to note that the results of Reaumur and Spallan- 

 zani were confirmed by Stevens of Edinburgh, who likewise employed 

 Reaumur's methods of investigation. Stevens experimented on a 

 "man of weak understanding who gained a miserable livelihood by 

 swallowing stones for the amusement of the common people." The 

 man was made to swallow perforated silver spheres containing animal 

 and vegetable food, raw and cooked, which were examined when void- 

 ed some 48 hours later. Similar experiments were made on dogs, the 

 contents of the hollow spheres examined after opening the animal's 

 C stomach. Stevens concluded that digestion is not the effect of heat, 

 ' trituration, putrification or fermentation alone, but of a powerful sol- 

 vent secreted by the glandular coat of the stomach. 



Summary: Summing up the progress made in the physiology of 

 digestion during the seventeenth and eighteenth centuries, probably 

 '--^ no one is more entitled to an audience than Sir Michael Foster ; "Dur- 

 ' , ing the two centuries the seventeenth and the eighteenth, physiologi- 

 \ cal inquiries, swayed now in one direction by views of chemical fer- 

 } mentation or effervescence, now in another direction by views of 

 ( mechanical trituration, had come in the end to the conclusion that 

 digestion was in the main a process of solution of a peculiar charac- 

 ter, begun and chiefly carried out in the stomach, though assisted by 

 minor subsequent changes taking place along the intestines. They 

 who were under the influence of vitalistic doctrines, and these were 

 < perhaps the more numerous, held the change ^o be the commencement 

 of, to be the first step in the conversion of food into living flesh and 

 blood, and spoke of it as a change differing from ordinary chemical 

 change, without being able to define the exact characters. It was left 

 ^ to the nineteenth century to throw new light on the nature of the 

 gastric changes and at the same time to show that what took place 

 in the stomach was not the whole digestion, but only the first of a 

 series of profound changes taking place along nearly the whole length 

 of the alimentary canal." 



