-i2 9 



Mercuric Chloride and Formalin. 



The author has used to good advantage the following 

 solution : 



Saturated aqueous solution of bichloride of mercury 100 parts 

 Formalin 4 parts. 



In this solution the tissues remain for 24 to 48 hours, 

 are then washed in flowing water for 24 hours, and the 

 hardening is completed in 70% (24 hours.) and 95% 

 alcohol. It is useful for hardening teeth, developing teeth, 

 developing bone, etc. 



Mercuric Chloride and Picric Acid Solution (Rabl). 



Saturated aqueous sol. of mercuric chloride 1 part. 



Saturated aqueous sol. of picric acid 1 part. 



Distilled water - 2 parts. 



This is excellent for hardening mammalian embryos. 

 The tissues remain in the fluid 8 to 12 hours, are then trans- 

 ferred to 70% alcohol until the picric acid is washed out 

 of the tissue; the hardening is completed in 95% alcohol. 



Mueller's Fluid (Heinrich Miiller). 



The fluid is made after the following formula: 



Potassium bichromate . . . . 2.5 parts. 



Sodium sulphate . . . 1 part. 



Water 100 parts. 



The potassium bichromate and sodium sulphate are 

 to be ground in a mortar. They dissolve quickly if the 

 water is heated. A large quantity of the fluid may be kept 

 on hand as it does not deteriorate by standing. Miiller's 

 fluid is especially to be recommended when large pieces are 

 to be hardened, but it must be remembered that the hard- 

 ening takes place very slowly. Pieces of about an inch 

 cube harden in 2 to 4 weeks, of two inches cube 1 to 

 months, and larger masses proportionately longer ; a human 

 brain for instance needs to be in the fluid from 6 to 8 

 months. Always use a large quantity of the fluid, and change 

 whenever it becomes turbid. Weigert recommends that the 

 jar containing the tissue to be hardened, especially if it be 

 the central nervous system, be kept in a warm oven at a 

 temperature of 30 to 40C. ; a spinal cord may in this way be 



