406 LIQUID PARTS OF ANIMALS. 



which just before its death had eaten a quantity of oats. It had 

 a yellowish colour, was transparent, but slightly opaline, mucila- 

 ginous, and thready like white of egg. It slightly reddened tinc- 

 ture of litmus, coagulated by boiling, even after having been di- 

 luted with water. It was therefore quite analogous to the pan- 

 creatic juice of the sheep.* 



From these experiments it follows that saliva and pancreatic 

 juice are different in their properties. 



1. The solid matter in pancreatic juice of the dog is at least 

 twice as great as that in saliva. 



2. Saliva contains mucus and salivin. If albumen or casein 

 be present, the quantity must be exceedingly minute ; but pan- 

 creatic juice contains a great deal of albumen and casein, and no 

 salivin or mucus. 



3. Saliva is usually slightly alkaline, but pancreatic juice con- 

 tains a little free acid. 



4. The saliva of the sheep and of smokers contains sulphocya- 

 nic acid, but there is no trace of it in the pancreatic juice of the 

 same animal. 



5. The presence of casein in pancreatic juice was inferred, be- 

 cause this juice is not only precipitated by acids but by metallic 

 salts and the tincture of nut-galls ; but as albumen is precipitated 

 by these reagents as well as casein, the evidence for the exist- 

 ence of this last substance is not satisfactory. Should its presence 

 be hereafter proved by experiment, it is not unlikely that its office 

 may be to remove the pepsin from the chyme, which may be ne- 

 cessary in order to its conversion into chyle. 



CHAPTER VI. 



OF BILE. 



THE bile is secreted by the liver, the largest of all the abdo- 

 minal viscera, and it makes its way into the duodenum by the 

 ductus communis choledochus. In man, the ductus communis and 

 the pancreatic duct usually enter the duodenum together, but in 

 the dog the pancreatic duct is commonly a good way lower 

 down than the biliary duct. 



* Recherches sur la Digestion, i. 26. 



