INTESTINAL DIGESTION. 13 



yellow (see Practical Part, Section VI.). During the change the liquid 

 shows, when examined spectroscopically, first two absorption bands near the 

 line D, which are due to the blue colour (cholecyanin], and subsequently a 

 single band between b and F, referable to the yellowish red colour (Jaffa's 

 choletelin). Bilirubin, or a body ^distinguishable from it, occurs in tissues in 

 which blood has been extravasated in rhombohedral crystals (called Haema- 

 toidin). 



Biliverdin (C 32 H 36 N 4 O 8 ) occurs along with bilirubin in the bile of man 

 and many animals, especially in those of which the bile is green. Its relative 

 quantity increases in inanition. Both colouring matters are met with in the 

 placenta of the bitch. 



Intestinal Digestion. 



Pancreatic juice is an alkaline liquid resembling saliva. 

 It is, however, of greater density, and probably contains no 

 globulin. It owes its activity to two ferments a diastatic 

 and a peptic both of which are contained in the precipi- 

 tate which is thrown down when pancreatic juice is treated 

 with alcohol. They can be extracted either from the 

 gland itself (Hiifner) or from the precipitate (v. Wittich) 

 by glycerine. From either extract a substance is precipi- 

 tated by alcohol, which, at the temperature of the body, 

 digests fibrin and other albuminous bodies in alkaline 

 liquids, and acts diastatically on starch. This substance is 

 called Pancreatin. It contains a proteid body, to which 

 the name Trypsin has been given by Kiihne, and to which 

 its peptic property appears to attach itself. From the 

 glycerine extract a substance containing the ferments is 

 precipitated by alcohol. Pancreatic juice emulsionizes and 

 decomposes neutral fats. 



It has lately been proved (Heidenhain) that the cell- 

 substance of the living pancreas is inert, but acquires 

 peptic activity by keeping, and more rapidly when acted 

 on by dilute acids. 



Proteids, subjected to pancreatic digestion, split into 

 two products, viz., a body having globulin properties, 

 and a peptone. The former passes into a peptone (called 

 by Kiihne antipeptone), which undergoes no further change 



