1888.] MICROSCOPICAL JOURNAL. 11 



processes adopted by other workers with the microscope. Nevertheless, it 

 must not be supposed that every stain and every process of staining recently 

 introduced into histology will be here described ; the space at my command 

 is too limited to enable me to perform so stupendous a task, nor should I do 

 so if it were otherwise. In contradistinction to some writers, I cannot help 

 thinking that during the last two or three years the subject of staining has 

 been rather overdone ; and I venture to believe that the processes which I am 

 about to detail, or modifications of these processes, will be found to admit of 

 a wide application, and that anyone possessing a knowledge of them will be 

 able to solve any problem in staining with which he may be confronted in 

 practical biological science. 



The art of staining tissues for microscopic examination may be advanta- 

 geously discussed under two heads, viz., single-staining and double or multiple- 

 staining. The first of these, involving only simple processes, and being the 

 only method known to and practised by the early histologists, is most prop- 

 erly treated of first. 



A recent writer, Arthur Bolles Lee, treats us, in his ' Microtomist's Vade- 

 Mecum,' to what appears to me to be a somewhat original notion as to the 

 purpose for which staining reagents are employed. LTnder the head of ' Theorv 

 of Staining' (page 38) he says : — ' The chief ends for which coloring reagents 

 are employed in zoo-histology is to obtain a nuclear stain of tissues, that is, a 

 stain in which nuclei, or, at most, the nuclei and their surrounding cell-proto- 

 plasm are colored, whilst the formed material of the tissues is left unstained. 

 That is what the histologist wants in the great majority of cases. He wants 

 either to differentiate the intimate structure of cells by means of a color reac- 

 tion, in order to study them for their own sake, or he wants to have the nu- 

 clei of tissues marked out b}^ staining in the midst of the unstained formed 

 material in such a way that thev form landmarks to catch the eye, which is 

 then able to follow out with ease the contours and relations of the elements 

 to which the nuclei belong ; the extra-nuclear parts of these elements being 

 expressly left unstained, in order that as little light as possible may be ab- 

 sorbed in passing through the preparation. Diffuse stains, or those which 

 stain formed material as well as protoplasm, are now more and more aban- 

 doned ; for instance, eosin, which was once a favorite stain, is now but little 

 used on account of the incorrigible diffuseness with which it stains. Except 

 for special purposes, such as the dyeing of thin membranes, which unstained 

 would be invisible, or for certain purely chemical ends, or for combination 

 with a nuclear stain to make a doiible-stain. diffusely-staining coloring agents 

 are not employed.' 



Whilst admittijig that the study of the germinal matter of cells is an im- 

 portant part of animal histology, I certainly cannot indorse Mr. Lee's tacit 

 theory that it is the chief branch of that science. Furthermore, it would 

 be instructive to learn how or by what means the eye can ' follow out with 

 ease the contours and relations of the elements to which the nuclei belong,' 

 when those elements are left unstained, and are therefore invisible in most 

 mediums. Surely microscopic preparations in which, "• at most,' the nuclei 

 and their surrounding cell-protoplasm were stained would be utterly worth- 

 less, except for the one special and not most important purpose, the study of 

 the development of the living matter of the cell. What the animal histolo- 

 gist really wants, in the majority' of cases, is by a single stain, or a combina- 

 tion of stains, to mark out clearly and sharply the particular characters 

 of both formed and forming tissue material, and the relation of different struc- 

 tures one to another; then, and then only, is he in a position to understand 

 the purposes which tissues serve, or the use for which they are intended, in 

 the living body. 



