DS 22 DS 22.10 



DYE STAINS OF SPECIAL APPLICATION 



433 



explanatory, tliough it must be enij)lia- 

 sized that only tliosc teclmiciuos arc in- 

 cluded in this division which are intended 

 for the specific staining of nuclear ele- 

 ments. General nuclear stains are given 

 under the headings DS 11 in Chapter 20. 

 Probably much annoyance will be caused 

 to cytologists by the grouping together, 

 in the second class, of mitochondria and 

 Golgi apparatus. It is not intended, of 

 course, by this grouping to suggest that 

 these are in any way related to each other. 

 They are, however, the chief ])reoccupa- 

 tion of the cytological cytologist, and the 

 techniques intended for their display may 

 therefore be justifiably included in the 

 same place. The ne.xt four sections deal 

 with a variety of cell inclusions too well 

 known to need further explanation at this 

 point; the final class has been erected to 

 contain all those miscellaneous techniques 

 w'hich have been designed to show not 

 only cell inclusions, but also such cell 

 extrusions as cilia, flagella, and the like. 



22.1 Nuclei 



For staining nuclei in cells any of the 

 techniques given in the last chapter 

 (DS 11) may be satisfactorily employed. 

 These nuclear stains are, however, by no 

 means the best when it is desired to bring 

 out for the interest or information of 

 students the various portions of a mitotic 

 figure other than the chromosomes them- 

 selves or when, for one reason or another, 

 it is desired to stain the chromosomes in a 

 manner which leaves them relatively 

 transparent. The majority of these tech- 

 niques have been developed by botanists, 

 but they may be applied equally well to 

 sections of animal material, and are de- 

 signed throughout to demonstrate clearly 

 all the elements, including the spindle 

 fibers, of a mitotic division. Most research 

 workers would prefer, probably, to retain 

 the iron-hematoxylin techniques to which 

 they are accustomed, but it is sincerely to 

 be hoped that the manufacturers of slides 

 for class purposes will learn of the existence 

 of other methods and will cease to sup- 

 ply the now inevitable iron-hematoxylin- 

 stained mitotic figure, which rarely shows 

 more than the chromosomes themselves. 



22.10 TYPICAL EXAMPLES 



Demonstration of mitosis in an onion 

 root tip using the rose bengal-orange 

 G-toluidine blue stain of Kedrovsky 

 1931 



Nobody who has i)repared onion root 

 tip for class demonstration by this meth- 

 od will ever be hkely to revert to the 

 iron hematoxylin metliod formerly cm- 

 ployed, for nothing is more attractive to 

 an elementary class than a polychrome- 

 stained specimen. 



Though the term o7iio7i root is usually 

 apphed to these preparations, there are 

 several members of the genus Allium 

 which will give better class-demonstration 

 material. The author's preference is for 

 the root tip of the leek {AlUu7n porrum), 

 which can be obtained just as readily as 

 the root tip of an onion. Excellent demon- 

 stration material can be obtained from a 

 leek seedhng about a month old. These 

 can be cultured in the laboratory, for 

 there is no objection to the etiolation 

 which results from the growing of such 

 material in improperly hghted surround- 

 ings. The high temperatures at which most 

 laboratories are maintained is also an ad- 

 vantage, since it causes a more rapid 

 growth and a greater variety of stages to 

 be obtainable in a single section. The 

 writer does not think that there is much 

 choice in fixative for these specimens, as 

 the mercuric-acetic-nitric fixative of Pe- 

 trunkewitsch (Chapter 18, F 3000.0014) 

 gives uniformly successful preparations. 

 The leek seedhng, upon being removed 

 from the soil, should be very, very thor- 

 oughly washed in normal saline solution 

 to remove adherent particles of fine grit 

 which would blunt the knife and the tip 

 of the seedling, with the roots attached, 

 is then dropped into a considerable vol- 

 ume of Petrunkewitsch's fixative. It may 

 remain here overnight before being re- 

 moved and thoroughly washed in several 

 changes of 50% alcohol. 



This material will present no difficulties 

 in sectioning. It is customary to cut a lon- 

 gitudinal section; and a section thickness 

 of from five to eight microns should be 

 employed rather than the conventional 

 ten microns. The sections are then at- 



