GENERAL TECHNIC 7 



twenty-four hours. thou[i;h tissues may remain longer without 

 injury. The alcohol should be changed after two or three hours. 

 This fixative should not be used where fine histological detail is 

 desired, since it causes some shrinkage. One advantage in its use is 

 the fact that tissues are hardened and ready for embedding at the end 

 of fixation. 



(2) Dilute Alcohol (30-per-cent. to 80-per-cent.). — This, as a rule, 

 gives unsatisfactory results, causing much shrinkage of the tissue 

 elements. 



(3) Formalin (2-per-cent. to lo-per-cent. aqueous solution). — 

 Formalin is rapid in its action and probably has better penetrating 

 qualities than any other fixative. For general purposes a lo-per-cent. 

 solution (i part commercial formalin to 9 parts water) should be 

 used. This fixes in from six to twenty-four hours. The results after 

 formalin are not always good, owing to the fact that it has little 

 hardening power, and the subsequent action of alcohol is likely to 

 cause some distortion of the tissues. It acts better when combined 

 with other fixatives than when used alone. (See Orth's fluid.) 



(4) Formalin-alcohol (Schaffer). 



Formalin, 30 c.c. 



Alcohol, 96-per-cent., 60 c.c. 



Tissues remain in this fixative about forty-eight hours and are then 

 placed in 96-per-cent. alcohol for a like period. 



(5) Muller's Fluid. 



Potassium bichromate, 2 . 5 gm. 



Sodium sulphate, i . o gm. 



Water, 100. o c.c. 



This fluid gives very good results, but is extremely slow in its action, 

 requiring from a week to several months. Fairly large pieces of 

 tissue may be fixed, but in all cases large quantities of the fixative 

 should be used and frequently renewed. 



(6) Orth's Fluid. 



MuUer's fluid (double strength), ] ^ 



r ■,. r. . r Equal parts. 



Formalm, 8-per-cent., j 



This is one of the best general fixatives. Its action is similar to that 

 of Miiller's fluid but much more rapid, fixation being accomplished 

 in from twenty-four to forty-eight hours, though specimens may 

 remain in the fluid several days wdthout disadvantage. Fairly 

 large pieces of tissue may be fixed with good results. The fixative 



