37G 



METHODS AND FORMULAS 



DS 20-DS 21 



the thionin-light green-orange G-erythrosin stain of Margolena 



1932 



Demonstration of parasitic fungi in tissue scrapings using the 



technique of Chahners and Marshall 1914 



23.31 Plants parasitic in plants 



23.32 Plants parasitic in animals 



23.33 Animals parasitic in animals 



23.34 Animals parasitic in plants 



23.4 Other zoological techniques 



23.5 Other botanical techniques 



24 Miscellaneous dye staining techniques 



DS 20 Dye-Staining Techniques of Special Application 



The phrase dye-staining techniques of 

 special application is here used in contra- 

 distinction to the dye-staining techniques 

 of general application which were given in 

 the last chapter. It must not be thought 

 that general techniques are incapable of 

 showing clearly any of the structures or 

 organisms, the special methods for which 

 have been transferred to the present chap- 

 ter. This chapter has only been organized 

 for the inclusion of those techniques which 

 are so specialized that they cannot justi- 

 fiably be employed for any other purpose 

 than those recommended for each. It has 

 been felt that, by the removal of these 

 techniques to a special chapter, it w^ould 

 be possible to avoid concealing what are 

 generally considered to be the techniques 

 of wide utility within a mass of special 

 methods. It will be emphasized again and 

 again, in the remarks under the various 

 headings below, that if one desires, say, 

 to stain chitin or plant skeletal tissues one 

 should look first among the generalized 

 techniques; and only when it has been 

 found that these are unsuitable, should 

 recourse be had to those in the present 

 chapter. 



These specialized techniques have been 

 divided into three large groups. The first 

 of these (DS 21) includes the techniques 

 for such histological elements as may be 

 required to be stained differentially. This 

 is followed by a section on cytological 

 elements (DS 22), wliich are defined for 

 the purposes of the present work as cell 

 inclusions not known to be organisms. 

 From time to time a confusion has arisen 

 between mitochondria and bacteria, and 

 there is undoubtedly at present some 

 disagreement as to whether some of the 

 small unidentified bodies — smaller than 

 bacteria — which occur in certain inverte- 

 brate cells are actually organisms or cell 

 inclusions of an unidentified function. The 

 third great division (DS 23) comprises 

 selective stains for specific organisms, the 

 majority of which are naturally bacteria 

 and their immediate allies; there are, how- 

 ever, a few other parasites, particularly 

 the fungi, the methods for the selective 

 demonstration of which are too specialized 

 for general use. To preserve continuity of 

 cross reference the dye stains in this 

 chapter are subdivided from DS 20, those 

 in the last chapter having been subdivided 

 from DS 10. 



21 SELECTIVE DYE STAINS FOR HISTOLOGICAL ELEMENTS 



The justification for this section is that 

 it is occasionally required, for purposes of 

 research or class demonstration, that some 

 special structure should be specifically 

 stained. The techniques given are not 

 intended as general-purpose stains and 

 their use should be confined to those cases 

 in which the demonstration of the particu- 

 lar tissue must outweigh all other con- 



siderations. The three histological ele- 

 ments which it is most commonly desired 

 to differentiate are: skeletal tissues (DS 

 21.1), both plant and animal, nervous 

 tissues (DS 21.2), commonly studied by 

 techniques inappUcable to other purposes, 

 and, to a lesser extent, certain special 

 stains for specific conditions in blood 

 (DS 21.3), which should be separated 



