APPENDIX. 

 Preparation of Sections — Method of Weigert. 



WHILE the Weigert technique is a standard histological 

 method, there are many modifications of it, with 

 some of which the brain of the rat is sometimes 

 rather refractory. The writer has usually obtained satis- 

 factory results by the following simple form of the method. 



The brain is removed from the skull as soon as possible 

 after death and is at once immersed in Miiller's fluid 

 (potassium bichromate, 2.5 gm.; sodium sulphate, 1 gm.; 

 distilled water, 100 c.c). This solution is renewed two or 

 three times during the first week, after which the material is 

 left undisturbed for two months or more, being kept in, the 

 dark during this time. The tissue is then washed for a few 

 hours in distilled water and passed into 50% alcohol for a 

 few hours more, after which it is transferred to 70% alcohol, 

 where it may remain for from twenty-four hours to several 

 weeks. It is next kept for twenty-four hours in each of 80%, 

 95%, and absolute alcohol successively, and passed through 

 cedar oil to parafftn. 



Serial sections 15/i-20iu thick are mounted on slides by the 

 ordinary water-albumin method. The parafBn is now washed 

 out of the sections by immersing the slide in xylol, from which 

 it is transferred to absolute alcohol. The slide is next flooded 

 with thin celloidin (0.5%), which is drained off and allowed 

 to dry in the air for a few minutes, and after this the slide 

 is passed rapidly down through a graded series of alcohols to 

 distilled water. 



The slides are placed upside down (supported on small 

 slips of glass) in a half-saturated solution of copper acetate 



