•THE-AlCimCOpE 



AM ii^^ypsyRATED 



Vol. XII. 



WASHINGTON, D. C, MAY, 1892. 



No. 5. 



On Imlbedding Animal Tissues in Paraffine for Sectionizing. 



By Prof. H. L. OSBORN, 



HAMLINE, MINN. 



This method of preparing animal tissues for sectionizing is de- 

 scribed in all books of microscopical technique, and the descrip- 

 tion presented here merely re^Deats from them without adding any 

 specially new features. Since every detail in this connection is 

 important, I will risk being tedious and attempt to give an ac- 

 count by following which anyone can be sure of success. Every 

 step of the process must receive careful attention to insure success. 

 The work can conveniently be subdivided into several parts. 



I . Fixing or Hardening the Tissue. — One of the best modes 

 of hardening is by the picro-nitric acid method. Prepare the 

 hardening fluid as follows : Dissolve picric acid crystals in distilled 

 water to saturation, add 2 per cent, of strong nitric acid ; a heavy 

 precipitate will fall ; filter and keep the filtrate for standard solu- 

 tion. Place in this standard solution, weakened with one-half or 

 two-thirds water, a piece of perfectly fresh tissue from a just killed 

 animal, or for small animals immerse the entire creature. Leave 

 it in from 3 to 6 hours. Then transfer it to 30 per cent, alcohol, 

 and in a few minutes thence to 50 per cent., and after an hour to 70 

 per cent. Keep it in 70 per cent., changing the alcohol daily till 

 no yellow^ color is imparted to the alcohol by the specimen. It is 

 then readv for staining:. 



3. Staining. — Prepare a solution of borax carmine as follows : 

 Carmine, i gramme ; borax, 4 grammes ; distilled water. ^6 c.c. 

 To this solution add its volume of 70 per cent, alcohol and filter. 

 The solution thus made will keep indefinitely. Immerse the spec- 

 imen after completion of hardening in the borax carmine solution. 



