358 APPENDIX. 



appropriate ground ; if the object is white or grey, 

 tlie slide should be placed on a piece of black paper ; 

 if it is dark, on a piece of white paper. Stained 

 sections should also be teased out against a white 

 or grey ground. 



Dissociating Fluids.- 



These are fluids which, whilst preserving certain parts 

 of a tissue, dissolve or partially dissolve othets, 

 principally the cementing or ground substances, so 

 that the former can be isolated by teasing or shaking. 

 As a rule the piece of tissue so treated should be 

 not more than one to two mm. square. 



Weak iodized serum, of a light brown colour is in most 

 cases the best. As the tissue absorbs the iodine, a 

 little strongly iodized serum should be added ; or 

 the fluid renewed. The tissue may often be teased 

 out after one day; but a longer time may be neces- 

 sary. 



Osmic acid, •! to 1 p.c.,is a dissociating fluid of general 

 application; it has the advantage of altering the 

 normal appearances in most cases very slightly. It 

 swells up some nuclei, and also the axis cylinders of 

 nerves. 



Dilute alcohol (30 to 35 p.c.) is also good for many 

 tissues. 



The following agents are also used, the tissues for 

 which they are most recommended are put in brack- 

 ets; baryta water (fibrillse of white fibrous tissue); 

 5 p.c. neutral ammonium chromate (mucous glands); 

 '02 p.c. potassium bichromate (muscle and nerve- 

 cells); "02 p.c. chromic acid (nerve-cells of spinal 

 cord); MuUer's fluid (olfactory cells); S p.c. chloral 



