304 NORMAL HISTOLOGY. 



preparing the sections for mounting. Loose sections can be stained, 

 etc., in porcelain butter dishes, being transferred with a bit of 

 platinum wire fused at one end into a glass rod. Such needles can 

 be readily bent to any desired shape and may be cleansed by passing 

 through a flame. 



1. Hematoxylin and Eosin. — Hematoxylin, the coloring-principle 

 of logwood, has proved a very useful stain for the nuclei of cells. It 

 is not a pure nuclear stain, but also tints the cytoplasm of cells and 

 the intercellular substances. It is most commonly employed in 

 combination with alum. Such combinations of coloring-matter 

 with a base are called " lakes." 



A hsematoxylin-lake may be used alone, or its use maybe preceded 

 or followed by the employment of a counterstain with some diffuse 

 color not affecting the nuclei. For counterstaining, eosin or neutral 

 carmine is usually employed. Both stain the tissues a diffuse red, 

 varying in depth according to the nature of the tissue-elements in 

 the section. 



There are several formulae for the preparation of alum-hsema- 

 toxylin, but that devised by Bohmer will answer all purposes, and 

 is very simple : 



1. Hematoxylin crystals, 1 gram. 

 Absolute alcohol, 10 cc. 



2. Alum, 20 grams. 

 Distilled water, 200 cc. 



> 



Cover the solutions and allow them to stand over night. The 

 next day mix them and allow the mixture to stand for one week 

 in a wide-mouthed bottle lightly plugged with cotton. Then filter 

 into a bottle provided with a good cork. The solution is then 

 ready for use. Nearly all solutions of alum-haematoxylin require 

 an interval of time for "ripening," and their stain ing-powers 

 improve with age. 



Alum-hsematoxylin is intended for staining sections from tissues 

 that have been fixed and hardened. It is especially useful when 

 the fixing-solution employed contained chromates, but may be used 

 after almost any method of fixation, if the time of staining is of 

 the right length and the sections are previously freed from acidity 

 bv thorough washing. 



If the following directions are closely adhered to, the student 



