PRESERVING AND PREPARING PATHOLOGICAL SPECIMENS. 53 



twenty-four hours, then, after thorough washing in water, they are put 

 for twenty-four hours in seveuty-per-cent alcohol, and then in strong 

 alcohol, in which they are kept. 



CORROSIVE SUBLIMATE. This is a most excellent fixative for deli- 

 cate structures. A convenient form is Lang's Solution. Its formula is: 



Mercuric Chloride, ( . .5 gms. 



Sodium " 6 " 



Ilydric Acetate, Glacial, 5 c.c. 



AVater, 100 c.c. 



The tissues should remain in sublimate solution, as a rule, not longer 

 than from one to three hours. 



Specimens fixed in sublimate develop a mercurial precipitate, do not 

 stain well, and become brittle unless the excess of sublimate is removed. 

 This can be largely done by prolonged washing in running water. But 

 it is much more easily and certainly accomplished by the chemical action 

 of dilute iodine solution. The specimen is removed from the sublimate 

 mixture and put at once into seventy-per-cent alcohol. To this is added 

 from time to time a sufficient quantity of saturated alcoholic solution of 

 iodine (or tincture of iodine) to give the alcohol a moderately deep 

 iodine color. At first this color gradually disappears, and the iodine 

 solution should be repeatedly added until the color persists. The speci- 

 mens are now transferred to seventy-per-cent alcohol, and after twenty- 

 four hours, to strong alcohol. 



Zenker^s Fluid is a good fixative and acts rapidly. It is a combina- 

 tion of Miiller's fluid and corrosive sublimate with acetic acid. Its 

 formula is: 



Potassium Bichromate, . . . ... . .2 parts 



Sodium Sulphate, . . . . . . . . . 1 ' 



Mercuric Chloride, . . . .*...' . . . . 5 " 



Hydric Acetate, Glacial, . . . . . . . . 5 " 



Water, ... . . < . . . . . 90 " 



The acetic acid should be added at the time of using, since the com- 

 plete mixture readily decomposes. Small pieces of tissue may be har- 

 dened in this solution in from twenty-four to forty-eight hours. They 

 should then be carefully washed and preserved in eighty-per-cent alcohol. 

 The use of iodine to remove the excess of sublimate, as described under 

 Lang's solution above, is desirable here also. 



Pathological specimens which occur, or are isolated in the form of 

 membranes, should be stretched with pins on a piece of wood or flat 

 cork before being immersed in the preservative fluids. Minute struc- 

 tures, such as occur in exudates from the mucous membranes and in 

 cyst fluids, renal casts, etc., may be hardened in Fleniming's osmic acid 

 mixture or in formalin followed by alcohol. Under these conditions re- 

 newals or changes of the fluids may be effected in tubes by the use of the 

 centrifugal machine. The specimens may finally be preserved in eighty- 

 per-cent alcohol. 



