272 METHODS OF ANALYSIS [Chap. 



tents of each beaker onto the filter and, when drained, wash twice with small quan- 

 tities of water. Combine the 2 extracts. 



(b) Hot water -aynmonium sulphate extract of blood. — Weigh out 30-35 grams of 

 fresh whole blood as caught from the animal into a porcelain mortar. Grind and 

 transfer to a 400 cc. beaker with hot water. Make up to about 150 cc. with boil- 

 ing water. Place over a flame, gradually bring to boiling, with constant stirring, 

 then add 20 cc. of 20% ammonium sulphate solution and continue boiling, with 

 constant stirring, for about 10 minutes. Decant onto an 18 cm. filter paper, re- 

 ceiving the filtrate in an 800 cc. beaker. Transfer the coagulum from the filter, 

 along with that remaining in the beaker, to a mortar. Grind to a smooth paste 

 and transfer to a beaker with boiling 35% ammonium sulphate solution. Make up 

 to about 50 cc. with the latter, stir for 8 minutes and again filter. Return the 

 coagulum to the mortar and grind again, transferring to the beaker as before with 

 boiling 31% ammonium sulphate solution. Repeat this process of 8 minute extrac- 

 tions of the coagulum in 33% ammonium sulphate solution and filtration as directed 

 above, v/ithout further grinding, until the filtrate measures about 450 cc. Wash out 

 each beaker twice with 8-10 cc. of hot 3§% ammonium sulphate solution, transferring 

 the coagulum and extract to the filter. Wash the coagulum twice with boiUng33% 

 ammonium sulphate solution from a wash bottle. Always allow the filter to drain 

 well between additions of extract or wash solutions. 



(C) Hot water-ammonhim sulphate extract of liver. — Weigh by difference from a 

 closed weighing bottle 15-20 grams of finely ground liver into a 400 cc. beaker. Add 

 a few cc. of cold water and beat up with a stirring rod to separate the particles of 

 tissue. Add enough boiling water to make the volume about 150 cc, place over a 

 flame and bring to boiling. Add 10 cc. of 20% ammonium sulphate solution and 

 continue to boil for 10 minutes. Allow to settle for a moment and decant the boil- 

 ing hot liquid onto an 18 cm. filter. Add 50 cc. of boiling water and stir for 8 min- 

 utes, without further heating, and decant onto the filter again. Repeat this addi- 

 tion of 50 cc. of hot water, stirring and decanting 8 times, returning the coagulum 

 to the beaker as soon as any considerable amount collects upon the filter. With 

 the eighth portion of water transfer the entire contents of the beaker onto the filter 

 and wash tv.-ice with hot water. Always allow the filter to drain well between 

 additions of extract or wash water. 



(d) Hot water-ammonium sulphate extract of brain. — Weigh out about 10 grams 

 of brain into a 250 cc. beaker. Add a few cc. of water and work up the brain and 

 water with a glass rod. Make up to about 100 cc. with boiling water, place over a 

 flame, and gradually bring to boiling, with constant stirring. While boiling vigor- 

 ously fnot before) add 20 cc. of 20% ammonium sulphate solution, boil gently for 

 about 10 minutes, allow to settle for a moment and decant slowly onto a linen filter 

 containing acid-washed, glassmaker's sand, receiving the extract in an 800 cc. 

 beaker. Add to the beaker containing the coagulum 50 cc. of 33% ammonium 

 sulphate solution, stir 1 minute, keep boiling and decant the liquid onto the filter. 

 Repeat this process of 1 minute extractions of the coagulum in 33% ammonium 

 sulphate solution, and filtration as directed above, until the filtrate measures about 

 450 cc. Wash out the beaker twice with 8-10 cc. of hot 3^% ammonium sulphate 

 solution, completing the transfer of the coagulum and extract to the sand, and v/ash 

 the coagulum twice with the wash solution. Always allow the filter to drain well 

 between additions of extract or wash solution. 



In making extracts of brain, give careful attention to the handling of the sample. 

 The coagulum is very soft. It should be stirred only enough to keep it in motion. 

 If handled roughly in returning from the sand filter to the beaker, it becomes too 



