ADVANCED CHEMICAL PHYSIOLOGY 313 



a band gradually develops in the blue, and that, along with the develop- 

 ment of this, the tint of the solution changes from violet to brown. 



To Prepare Pure Glycocholic Acid. In certain districts of 

 Germany and America it has been observed that the glycocholic 

 acid can be separated from the bile by a very simple process, and, 

 so far as it has as yet been tried, the bile obtained from oxen reared in 

 this country appears to be suitable for the process. The method is as 

 follows : 



Some ox bile is placed in a stoppered cylindrical vessel, and mixed 

 with ether and hydrochloric acid in the proportion of ten parts of the 

 former and four parts of the latter, for every hundred parts of bile. A 

 few crystals of glycocholic acid are added to the mixture so as to start 

 the crystallisation, the vessel is stoppered, vigorously shaken, and then 

 allowed to stand in a cool place. After some time the mass will be 

 found to be " solid " with crystals. These are collected in a filter 

 paper, and washed with cold distilled water till no more pigment can be 

 removed. They are then removed to a flask and dissolved in boiling 

 water ; the solution is filtered hot, and the filtrate, on cooling, deposits 

 numerous acicular crystals of the acid. These may now be collected, 

 washed with distilled water, and dried (see p. 236). 



Preparation Of Taurin. Bile from carnivorous animals cat or dog 

 is heated on a sandbath with one-third its bulk of concentrated hydro- 

 chloric acid until a resinous-like mass of the anhydride of cholalic acid 

 (called Dyslysin) has formed. This can be drawn out into brittle threads 

 by means of a glass rod. The dyslysin is filtered off, and the filtrate is 

 evaporated to a small bulk, the sodium chloride, which crystallises out 

 during the evaporation, being removed by filtration. The thin syrup 

 is then poured into fifteen times its bulk of alcohol, and left standing 

 twenty-four hours, when the taurin will have crystallised out. It 

 can be purified by collecting the crystals on a filter paper, arid washing 

 with cold water. 



CHAPTER XXII 

 BLOOD 



Preparation of Fibrin Ferment. Blood serum or defibrinated blood 

 is mixed with twenty times its bulk of alcohol. A copious white 

 precipitate is obtained. Allow this to stand under alcohol for six to 

 eight weeks. All proteins other than fibrin ferment are coagulated. 

 Decant fluid, collect the precipitate on a filter and after all alcohol has 

 drained off grind the precipitate in a mortar with water. The watery 

 extract which can be filtered contains the fibrin ferment. 



Estimation of the Coagulation Time (Dale and Laidlaw). Prepare a 

 number of capillary tubes about 2 cm. long with an internal diameter of 

 1-3 to 1-4 mm. Narrow one end of a capillary tube (best to prepare a 

 number at one time as they only serve for one estimation) in the flame, 

 insert into the bore of the tube by the open end a leaden shot of a weight 

 of approximately 9 mgm. Such a shot should move easily, rolling the 

 whole length of the tube. Now narrow the open end of the capillary 

 to prevent the shot falling out. The shot should be clean and round. 



To carry out the estimation from a prick in the finger fill a capillary 

 tube by bringing one end into contact with the drop of blood, the tube 



