312 HISTOLOGICAL TECHNIQUE. 



The hematoxylin crystals may be dissolved in the alcohol and 

 the solution kept in stock, the proper proportions of lithium carbon- 

 ate solution and water being; added at the time of use. 



3. Wash in water to which a little lithium carbonate solution has 

 been added (about 2 cc. to each 100 cc. of water). The sections 

 should acquire a deep-blue color. 



4. Differentiate in 0.25 per cent, solution of potassium perman- 

 ganate in distilled water, till the gray matter — e. g., of the spinal 

 cord — becomes brownish-yellow (one-half to five minutes). 



5. Decolorize the gray matter in the following solution : 



Oxalic acid, 1 gram, 



Potassium sulphite, 1 



Distilled water, 200 cc. 



6. Wash thoroughly in distilled water. 



7. Dehydrate in 95 per cent, alcohol. 



8. Clear in carbol-xylol, oil of bergamot, or oil of origanum. 



9. Mount in xylol-balsam or xylol-dammar. 



This method stains the myelin-sheaths of the medullated nerve- 

 fibres a dark blue, nearly black, color. If it has been preceded by 

 a stain with neutral carmine, the axis-cylinders of the nerve-fibres- 

 will be stained red, and the nuclei of the nerve-cells will also 

 appear red. 



14. Golgi's Methods. — These methods have yielded most excel- 

 lent results in the study of the central nervous system, the dis- 

 tribution of the peripheral nerves, and the delicate terminations- 

 of the ducts of glands; e.g., the bile-capillaries. The methods 

 must be regarded as special procedures in such studies, and can 

 but be referred to here. They all depend upon hardening in some 

 chromium salt, with or without the addition of osmic acid, and the 

 subsequent impregnation with silver nitrate. A precipitate is thus 

 produced on or within certain of the elements in the specimen, giving 

 them a dark-brown or black color. The methods are capricious, 

 and not all of the tissue-elements of like character in the specimen 

 are rendered prominent. This is an advantage, but necessitates 

 a degree of care in the interpretation of the results. Furthermore, 

 irrelevant precipitates may form in the tissues which have no 

 definite relations to any structure. Considerable practice is, there- 

 fore, required for the successful employment of all these methods,. 



