302 ' Medicine, [Chap. IV. 



digestion, and that they mutually assist each 

 other. 



Spallanzani's next experiments were directed 

 to animals possessing what he called intermediate 

 stomachs ; such as are endowed with muscles less 

 thick and strong than the former, but more so 

 than the membranous stomachs. Among these he 

 examined and made experiments upon the raven, 

 the crow, the heron, and many other birds, which 

 have this intermediate structure of the organ in 

 question. It was found in these birds, as might 

 be expected, that digestion is performed by a more 

 equal combination, than in the former cases, of the 

 forces of muscular action and a gastric menstruum 

 secreted for the purpose. 



These interesting experiments on digestion were 

 finished with those animals which have thin mem^ 

 braneus stomachs. This class comprehends an im*- 

 mense number of species, as man, quadrupeds,^ 

 fishes, reptiles, &p. No triturating power is pos- 

 sessed by the stomachs of this description ; for their 

 muscular fibres seem to exert little other effect 

 than that of propelling their contents through the 

 pylorus. In proof of this is alleged the well known 

 fact, that cherries and grapes are often received and 

 voided entire from the human alimentary canal. 

 The solvent power of the gastric liquor in these 

 animals was found almost solely to effect the dis- 

 solution of food, after the preparatory treatment 

 of mastication, and the admixture of saliva. To 

 prove the efficacy of this powerful agent in the 

 process of digestion, Spallanzani enclosed different 

 kindii of animal and vegetable food in linen bags. 



