LESSON VIII. 



RAPID HARDENING. STAINING IN BULK. 



1. The fixing and hardening of tissues preparatory to cutting 

 sections must be carried out slowly if the best results are to be 

 obtained (cp. p. 295). But it is sometimes desirable to obtain 

 sections on the day on which the tissue is removed from the 

 body. In such cases the freezing method described above (p. 49) 

 may be employed, or the preparatory hardening process may be 

 shortened, as in the methods given below. They give satisfactory 

 results with certain tissues only. 



a. Throw a small piece of the tissue into boiling water, and 

 leave it for one to two minutes, just sufficient to coagulate the 

 proteids. (Try tongue of mammal, heart of frog, or muscular 

 tissue.) 



b. Place a piece of tissue, not larger than 4x4x2 mm., in 

 O5 or 1 p.c. osmic acid for half-an-hour, pass through water and 

 alcohols leaving 5 to 10 minutes in each ; leave in absolute 

 alcohol half-an-hour. This will only serve for a small piece of 

 tissue, since the osmic acid penetrates slowly. (Try nerve or 

 ganglion.) 



c. Use Flemming's fluid instead of osmic acid. (Try liver 

 of frog.) 



d. Place a small piece of tissue in a saturated solution of 

 mercuric chloride in 95 p.c. alcohol. Leave for 1 hour, wash in 

 95 p.c. spirit. Place for an hour in absolute alcohol coloured 

 brown with iodine dissolved in potassic iodide. (Mammalian 

 liver, kidney or same tissues as in (a).) 



