INTRODUCTION. 5 



hardened in alcohol. The composition of these 

 mixtures is as follows : 



a. Osmic acid, I % solution . . .10 parts. 

 Chromic acid, I % solution . . .25 parts. 

 Hydric acetate, 2 % solution. . . 5 parts. 

 Water ....... 60 parts. 



b. Chromic acid, I % solution . . .25 parts. 

 Hydric acetate, 2 % solution . . 5 parts. 

 Water ....... 70 parts. 



The second mixture gives the best results with 

 haematoxylin staining. 



Potassium Bichromate. This salt is used in a 

 two-per-cent. aqueous solution, or more generally 

 in the form of Milllers fluid, the composition of 

 which is as follows : 



Sodium sulphate . . . . . . I part. 



Potassium bichromate . . 2 to 2. 5 parts. 



Water ...... 100 parts. 



Picric Acid. This agent, while hardening, pre- 

 serves the structure of many tissues very perfectly,* 

 and at the same time stains them yellow. It is usu- 

 ally necessary to complete the hardening with alco- 

 hol. For the decalcification of bone it is one of the 

 best of agents, although it acts very slowly. It is 

 used in saturated aqueous solution. 



Osmic Acid. This substance has the power of 

 fixing and hardening the tissue elements in a nearly 

 normal form, and is one of the most valuable of this 

 class of agents. It gives tissues a gray or brown ap- 



