382 LIBBIE H. H V.MAN. 



developed. One should never try to pull the sections A and C 

 forcibly apart. After screwing the clamp tightly, the sections 

 C plus D are withdrawn from B, the apparatus being held inverted 

 during the whole of the procedure to prevent the spilling of the 

 contents of C plus D. The contents are immediately poured 

 into a small graduated tube and the volume noted. Gradu- 

 ated centrifuge tubes have been found very convenient for this 

 purpose. A little practice with the apparatus is required to 

 prevent the spilling of the water from C plus D and a tube 

 should be at hand to receive this water just as C is withdrawn 

 from B. The portion A plus B is now analyzed by Winkler's 

 method and the blanks which consist of only A plus B are 

 analyzed at the same time. The clamp around B in each tube 

 is open and o.i cc. of each of the reagents used in Winkler's 

 method is added. The clamp is then closed, the contents shaken, 

 the precipitate allowed to settle as usual, and after again opening 

 the clamp, o.i to 0.2 cc. concentrated HC1 added carefully so -as 

 not to disturb the precipitate. The clamp being again closed, 

 the tube is shaken to dissolve the precipitate and the contents 

 are then poured into a small evaporating dish and titrated with 

 sodium thiosulphate. The latter should be about 1/500 normal. 

 With greater dilution of the thiosulphate the end point becomes 

 uncertain. The volume of the tube A plus B must then be 

 determined. If care is taken not to move the clamp around B 

 during the preceding operations, the tube A plus B can be filled 

 with water of the same temperature as that obtaining during the 

 experiment, the clamp closed, excess water at the top removed, 

 and the contents then poured into a graduated tube. In my 

 experience the volume of A plus B and C plus D must be deter- 

 mined at each experiment as they vary slightly owing to varia- 

 tions in the position of the clamp when the two portions are 

 separated. One must remember to subtract 0.2 cc. from the 

 volume of A plus B, to compensate for the loss of this amount 

 of water when the reagents are added. 



In calculating the results, it must be borne in mind that only 

 the portions A plus B are analyzed while the animal respired 

 from A plus B plus C plus D. The thiosulphate equivalent of 

 each cc. of A plus B is calculated and from this the thiosulphate 

 equivalent of the entire apparatus is obtained. It is thus neces- 



