GROWTH OF THE CORPUS CALLOSUM 37 



b. The method of procedure 



The material was obtained from seventy-six albino rats (fifty 

 males, twenty-six females), all from the rat colony at The Wistar 

 Institute. Each rat was chloroformed and notes made on the 

 age, sex, body weight, and body length. After dissection the 

 entire brain was severed from the spinal cord at the level of the 

 calamus scriptorius and weighed to a milligram in a closed 

 weighing bottle. The brain was next transferred to a 10 per 

 cent formalin solution for from twelve to sixteen hours at room 

 temperature, the basal surface of the brain being in contact 

 with the bottom of the vessel. Then sagittal sUces, which con- 

 tain the entire callosum — about 3 mm. in thickness and includ- 

 ing the plane from which the section was to be taken — were 

 placed in Weigert's rapid mordanting fluid for from four to five 

 days. After being washed with running water and passed 

 through the alcohols, they were put in ether-alcohol for a day 

 and then imbedded in parlodion. A short series of sagittal 

 sections 20^ thick was cut so as to include one in the median 

 plane, which was used for study. These were treated by the 

 Kultschitzky-Wolter's myelin stain method, modified shghtly to 

 obtain the best results from this particular tissue. In detail the 

 modified method is as follows: 



After cutting in 70 per cent alcohol, the sections were passed 

 to distilled water, then mordanted in Kultschitzky's fluid for 

 twelve hours at a temperature of 37°C. They are then well 

 washed with tap-water, and brought into a decolorizing solution 

 composed of 



parts 



Borax 2.0 



Ferricyanide of potassium i. 2.5 



Aqua distillata 200.0 



They were kept in this solution from ten to twenty minutes, 

 or until complete differentiation of the fibers, and then were 

 well washed with running water, dehydrated, cleared with creo- 

 sote, and mounted in neutral Canada balsam. 



