184 APPENDIX. 



fluid 30 minutes to an hour,, then 24 hours in 70$ alcohol, and 

 finally place in 90$ alcohol. 



Schultze's Macerating Fluid. Dissolve a gram of potassium 

 chlorate in 50 c.c. of nitric acid. The tissue should be boiled in 

 the mixture and afterwards thoroughly washed in water. 



Schultze's Solution. Dissolve zinc in pure hydrochloric acid, 

 evaporate in the presence of metallic zinc, on a water-bath, to a 

 syrupy consistency, add as much iodide of potassium as will dissolve, 

 and then saturate with iodine. (When heated with this fluid cellu- 

 lose turns blue.) 



Section-cutting. Many objects can be cut by hand with a razor 

 (which must be very sharp). The object should be held in the left 

 hand while the razor is pointed away from the body, and allowed to 

 rest on the tips of the fingers with its edge turned towards the left. 

 It is then drawn gently towards the body so as gradually to shave 

 off the section. Small objects may be held between two pieces of 

 watchmaker's pith previously soaked in water. In either case the 

 razor should be kept wet. 



Many objects, however, require more careful treatment by one 

 of the following methods: 



A. Paraffin MetJiod. After hardening and staining, the object 

 is soaked in strong alcohol (95$ or more) until the water is thor- 

 oughly extracted (2-12 hours, changing the alcohol at least once), 

 then in chloroform until the alcohol is extracted (2-12 hours), and 

 then in melted paraffin (not warmer than 55 C.) on a water-bath 

 for 15 to 30 minutes (too high a temperature or too long a bath 

 causes excessive shrinkage). Some of the paraffin is then poured 

 into a small paper-box, or into adjustable metal frames. The 

 object is transferred to it and after the mass has begun to set it is 

 placed in cold water until quite hard. It is then cemented (by 

 paraffin) to a square piece of cork and placed in the section-cutter 

 or microtome. 



The sections may be cut singly wifch the oblique knife or by the 

 ribbon-method,* the knife being kept dry in either case. In mount- 

 ing they should be fixed by the collodion-method. (See Collodion 

 and Clove -oil.) 



B. Celloidin Method. This is especially applicable to delicate 

 vegetal tissues. After dehydrating the object thoroughly in alco- 

 hol, soak it 24 hours in a mixture of equal parts of alcohol and ether. 

 Make a thick solution of celloidin in the same mixture and soak 



* See Whitman, 1. c., p. 71. 



