METHODS OF RESEARCH: FLAGELLA STAINING 119 



important is the right length of exposure to the mordant and 

 then the right length of exposure to the stain Only some such 

 very general directions can be given because a method that will 

 succeed with one organism often ; ails entirely with another The 

 student should consult the various text books and then go ahead. 

 We have had excellent results on a variety of organisms using 

 half a dozen different staining methods. 



Special Stains. — For method of staining spores and capsules 

 consult the various text books. The opposition to the use of mor- 

 phological differences for classifying bacteria has come largely, 

 I believe, from persons who are not naturalists and who have 

 had indifferent success in staining bacteria. 



CARE OF SPECIMENS 



In many institutions there exists a discreditable lack of 

 thoroughness in the preservation of interesting specimens, and 

 those persons who throw away good pathological material are 

 usually the very ones who have described it badly to begin with, 

 so that between an imperfect description and entire absence of 

 the materials on which the description was founded, the system- 

 atist can only guess what was the real state of the case. Some- 

 times when a laboratory changes heads the collections of the 

 first man are destroyed by the second. I have known one shock- 

 ing case of this kind. The student should remember that 

 whatever is worth describing is also worth preserving. The col- 

 lections of a pathological laboratory, if well made, become of 

 greater and greater importance as time passes. They should 

 include the following groups of material. 



Herbarium Specimens. — These are to be fastened on sheets 

 of stiff white paper of the standard herbarium size, and properly 

 labeled, one sheet being devoted to each parasite, but the more 

 specimens of it the better, especially if they are from different 

 localities. 



Coarse Dried Material. — Limbs, trunks, and other material 

 too cumbrous for the herbarium sheets should be properly 

 ticketed and stored in tight boxes or in glass cases. This 

 material and the herbarium sheets must be examined frequently 



