326 APPENDIX 



with osmic acid is not soluble in alcohol (oleic acid may be to a 

 slight extent), and as the yellow-brown granules spoken of above 

 become black in alcohol, the tissue may be kept in alcohol, best 

 75 to 80 p.c., for some days before being cut. It is safest to cut 

 the tissue frozen ; but it may be imbedded in paraffin and cut, 

 provided it has been kept some time in alcohol. Fat treated 

 with osmic acid is soluble in turpentine, less soluble in xylol, 

 still less in benzin, clove oil, chloroform : the solubility in these 

 reagents decreases as the tissue is kept in alcohol. 



Fat globules in sections of tissues which have been hardened 

 in Miiller's fluid, formol or other aqueous solution, and which 

 have not been treated with alcohol, may be stained by placing 

 them in 1 p.c. osmic acid for some hours to a day, or in Marchi's 

 fluid in the warm. For staining with Sudan in, and quinoline 

 blue, cp. p. 80. 



MUCIN. 



Whether mucin stains or not depends upon the hardening 

 agent used, and upon the way in which the stain is applied ; 

 speaking generally mucin is not stained by acid coal-tar colours, 

 and is stained by basic coal-tar colour? (cp. p. 162), but none of 

 these is a specific stain for mucin. 



The following methods may be used : 



Tissue hardened in alcohol. Sections are fixed on the cover- 

 slip, passed down to water, placed for about a minute in poly- 

 chromatic methylene blue, washed in acidified water, placed for 

 about 30 sees, in 10 p.c. potassium bichromate, passed quickly 

 through absolute alcohol to bergamot oil, then mounted (Unna). 



Tissue hardened in mercuric chloride. Sections are fixed to 

 the slide, passed down to water, left 3 to 5 minutes in 5 p.c. 

 aqueous mercuric chloride, placed in weak thionin solution 10 to 

 15 minutes, passed through alcohols, and cedar- wood oil, to balsam 

 (Hoyer). 



