FIXATION 641 



For the dissociation of muscle fibres small cubes (0.25 to 0.5 cc.) 

 are placed for ten to thirty minutes in the following solution : 



Strong nitric acid 100 cc. 



Potassium chlorate, sufficient to saturate. 



The bits of tissue should be handled with glass rods. After 

 some minutes they begin to disintegrate at the surface, and should 

 then be transferred to running water, where they are left to wash 

 for three to twelve hours. The pieces of tissue are then transferred 

 to a mixture of equal parts of alcohol, glycerin, and water, and thor- 

 oughly shaken. Muscle fibres isolated in this way may be kept for 

 months. 



Epithelium may be dissociated by teasing or by the action of a 

 40 per cent, solution of potassium hydroxid, or by means of a 10 to 

 20 per cent, aqueous solution of "lysol," and preserved, if desired, 

 in the mixture of alcohol, glycerin, and water. 



For the isolation of nerve cells bits of the anterior horns of the 

 spinal cord or other grey matter of the central nervous system may 

 be treated in a similar manner. They may also be isolated by im- 

 mersion in a 0.2 per cent, aqueous solution of " formalin" in nor- 

 mal salt solution for two to twenty-four hours (Gage *), or in a 0.2 

 per cent, aqueous solution of potassium bicarbonate, two to five 

 days. Afterward they are transferred to a normal saline solution 

 or to the mixture of alcohol, glycerin, and water, and isolated by 

 shaking, assisted, if necessary, by gentle teasing. 



Similar preparations may also be made by placing small bits of 

 tissue in 30 per cent, alcohol for two days or more ; then shake 

 thoroughly, allow the debris to settle, remove a drop of the fluid 

 with a pipette, and examine. 



Any of the above preparations may be stained by the addition 

 of a small drop of a solution of eosin, picro-carmin, or methyl 

 green to the fluid in which they are examined. 



FIXATION 



For the preservation of tissue, and as a preparation for further 

 manipulation, most tissues require to be " fixed." Innumerable 

 formulas have been advocated for this purpose, many of them hav- 

 ing as their object the demonstration of certain structural features 

 by the after application of special staining methods. 



The action of the fixing fluids is in most cases dependent upon 



* Vertebrate Histology, 1900. 



