412 JAMES STUART PLANT 



whole was kept in a black cardboard case in a dark closet. 

 Subsequent weighings were as follows. The brain was removed 

 from the solution and placed for about ten seconds on a dry- 

 piece of filter-paper. The string by which it had been suspended 

 was during this time removed. The brain was then placed on 

 a watch-glass and immediately weighed. It was returned to the 

 Miiller's fluid as quickly as possible. The watch-glass was then 

 weighed. Reweighings were carried out at 24 hours, and at 7, 

 14, 30, and 75 days after killing the rat. On completion of the 

 weighings the percentage of water in the brain at the final weigh- 

 ing was determined. This procedure involved placing the 

 brain, immediately after its last weighing, in a small glass vial 

 of known weight. This was kept in a drying oven (temperature, 

 97°) for one week. On removal, the vial was cooled in a desic- 

 cator at room temperature and weighed. 



The Mtiller's fluid used was made up in 1000 cc. lots. To 

 25 grams of potassium bichromate c. p. and 10 grams of sodium 

 sulphate c. p. was added 1000 cc. of distilled water. Time was 

 given for dissolving the salts and, after thorough agitation, the 

 solution was divided into two '500 cc. lots and kept for one month 

 before being used. In every instance 'pairs' of brains were 

 fixed in fluid from the same bottle. The Miiller's fluid was 

 always kept in a dark closet. 



No attempt was made to control the temperature during the 

 reaction of fixation other than that all specimens were kept in the 

 same dark closet at room temperature. Thus the results may be 

 considered as comparable. 



Necessarily our original results are in terms of absolute weights 

 and absolute gains. In the presence of so diverse initial weights 

 it seemed, however, best to state all gains in weight as percent- 

 ages of the original weight. This makes the data comparable. 

 Corresponding to this, all statements of the relation of one 

 brain's gain to that of another are in terms of a percentage of 

 the percentages of gain of the heavier brain. This leads to 

 higher figures, in the relations of the gains, than would be the 

 case were the actual differences between the absolute gains 

 stated. 



