216 The Physiology of Digestion [lect. 



Putrefaction in Spallanzani's time, as of old, was regarded 

 as one of the modes of fermentation; but by his time the 

 general ideas about fermentation had become more clearly 

 defined. It was no longer confounded with the effervescence 

 due to mere chemical action. " There are," says Spallanzani, 

 " three kiuds of fermentation : the vinous or sweet, the acetous, 

 "and the putrid." The action of the gastric juice was not a 

 putrid fermentation ; could it be one of the other two ? He 

 was inclined to believe that the action could not be considered 

 as any kind of fermentation at all, because bubbles of air 

 formed a necessary feature of every fermentation in a liquid, 

 and solution by gastric juice could and generally did take 

 place without any bubbles of gas being formed. The action 

 certainly was not a vinous fermentation, since neither gas nor 

 alcohol was formed. Could it be of the nature of acetous 

 fermentation ? In discussing this Spallanzani enters on the 

 question whether gastric juice is acid. 



It will be remembered that though van Helraont had put 

 in the foreground the acid nature of the digestive fermentation 

 taking place in the stomach, succeeding writers had denied 

 this and did so as time went on with increasing assuredness, 

 though Spallanzani as we have just seen referred to its being 

 still maintained by some. Spallanzani's results led him to 

 agree with the dominant view. It may here be remarked 

 that when Spallanzani speaks of gastric juice he means some- 

 thing which he regards as a mixed fluid. The juice which he 

 squeezed out of the sponges contained in the tubes recovered 

 from the stomach he describes as "a transparent yellow fluid 

 " which gave very little sediment on standing, which had 

 " a taste intermediate between bitter and salt, which was not 

 "very volatile and which certainly contained no inflammable 

 " components." When on the other hand he opened the 

 stomach of dogs and examined the liquid which oozed out 

 from the surface of the lining mucous membrane, he found 

 that this was " colourless, insipid and very thin," thus con- 

 trasting with that which is generally found in the interior 

 of the cavity of the stomach when opened, this being yellow, 

 bitter and somewhat gelatinous, like the material imbibed by 



