182 NATURAL THEOLOGY. 



ceived that churning in the lungs which is proba- 

 bly necessary for the intimate and perfect union 

 of the old blood with the recent chyle. Who 

 could have dreamt of a communication between 

 the cavity of the intestines and the left great vein 

 of the neck ? Who could have suspected that this 

 communication should be the medium through 

 which all nourishment is derived to the body, or 

 this the place where, by a side inlet, the impor- 

 tant junction is formed between the blood and the 

 material which feeds it ? 



We postponed the consideration of digestion, 

 lest it should interrupt us in tracing the course of 

 the food to the blood ; but in treating of the ali- 

 mentary system, so principal a part of the process 

 cannot be omitted. 



Of the gastric juice, the immediate agent by 

 which that change which food undergoes in our 

 stomachs is effected, we shall take our account 

 from the numerous, careful, and varied experi- 

 ments of the Abbe Spallanzani. 



1. It is not a simple diluent, but a real solvent. 

 A quarter of an ounce of beef had scarcely touch- 

 ed the stomach of a crow, when the solution 

 began. 



2. It has not the nature of saliva; it has not the 

 nature of bile ; but is distinct from both. By ex- 

 periments out of the body, it appears that neither 

 of these secretions acts upon alimentary substan- 

 ces in the same manner as the gastric juice acts. 



3. Digestion is not putrefaction ; for the digest- 



