396 PKACTICAL PHYSIOLOGY 



crystallisation commences, when the basin is removed and allowed to stand. 

 The crystals (glistening plates) are collected on a filter, and, to purify them, may 

 be recrystallised. 



A solution of the crystals gives the bromine and the glyoxylic reactions very 

 distinctly, and if the crystals be heated in a test tube indol and skatol (see p. 406) 

 are evolved. 



Ellinger has shown the constitution of tryptophane to be indolamino-propionic 

 acid ; its formula is probably : 



C -CH 2 -CH(NH 2 )-COOH 

 C 6 H 4 <^ ^>CH (a. amino-propionic acid) 



NH 

 (Indol group.) 



Tryptophane is the mother substance of indol, which, along with its methyl 

 derivative skatol, is largely responsible for the faecal colour. These bodies are 

 produced from tryptophane by bacterial growth (see p. 405). 



Preparations of trypsin have a rennin-like action on milk if sufficient 

 calcium be added (see p. 327). 



II. Amylopsin, Pancreatic Amylase. This ferment acts on starch 

 in exactly the same way as ptyalin does i.e. it converts it into 

 maltose and achroodextrin. Unlike ptyalin, it is capable of acting on 

 unboiled starch. 



EXPERIMENT VII. Add some glycerine extract of pancreas to some 

 powdered starch. Shake, and place in the water-bath at 37. Eemove 

 drops every half minute, and mix on a slab with a drop of iodine 

 solution. Note the appearance of the dextrine reaction. When this 

 disappears, apply Trommer's test, or one of its modifications, to a, 

 sample of the digest; note the reduction due to maltose. 



III. Steapsin or Lipase. This decomposes neutral fat into fat 

 acid and glycerine (see Fats, p. 314). 



EXPERIMENT VIII. Some minced pancreas is shaken with water 1 

 strained through muslin, and the resultant extract divided into two 

 parts. One of these is boiled to destroy the ferment, and is then 

 cooled. To both portions (about 10 c.c. each) are added five drops of 

 melted and filtered butter fat, a few drops of an alcoholic solution of 

 phenolphthalein, and then N/10 caustic soda, until a deep red colour is 

 obtained. After vigorous shaking, so as to obtain a partial emulsion, 

 the test tubes are placed in the incubator, and examined after about 

 half an hour. The lipase-containing fluid will be decolourised (the 

 fatty acid having bleached the phenolphthalein), and, to regain the 

 original red colour, a certain number of c.c. N/10 caustic soda must be 

 added to it. In this way, an approximate estimate can be obtained of 



1 Glycerin does not dissolve steapsin, so that a glycerine extract of pancreas ia 

 not suitable for this experiment. 



