xlii INTRODUCTION. 



METHODS OF STAINING TISSUES. 



TISSUES may be stained with certain reagents, e.g. eosin, which give a uniform colour to the 

 section, whilst other substances derive their value from staining different parts of a section 

 unequally ; nuclei, for example, are usually stained of a deeper red than the surrounding 

 protoplasm. For the method of transferring large sections to a slide, see p. xxvi. 



GENERAL DIRECTIONS. 



It is always advisable to use rather a weak solution of the staining agent, as this stains 

 slowly and gives the dye time to completely permeate the section. When practicable the 

 sections should remain in the fluid for several hours. The proper depth of tint can easily be 

 ascertained by lifting out a section and washing it in water, and examining it on a slide with 

 a low power. A little practice soon enables one to tell when the staining is deep enough. 

 For class purposes, however, it is often necessary to use strong solutions of the dyes, and 

 the results are very satisfactory. 



For class purposes staining with a strong dye is readily accomplished. Float a section on 

 to a slide (p. xxvi), remove all the water from the slide and around the section. Place on the 

 section a large drop of the staining fluid, and leave it 'until the section is properly stained. 

 Wash off the surplus pigment in a bowl of water, float the section on to the slide again, and 

 mount it in glycerine or other mounting fluid. 



STAINING SOLUTIONS. 



LOGWOOD SOLUTIONS. 



(a) A. Dissolve '3 grms. of haematoxylin in 10 c.c. of absolute alcohol. B. Dissolve -3 

 grms. of alum in 100 c.c. water. A few drops of A added to a few c.c. of B gives a solution 

 of a beautiful violet colour, which rapidly stains tissues. 



() A strong infusion of logwood chips is made ; to this reddish-coloured fluid, after filtra- 

 tion, alum is added, until a bluish-violet solution results. The violet colour deepens by ex- 

 posure to the air for several days. 



(c) Take 60 grms. of extract of haematoxylin and 180 grms. of alum. Rub them toge- 

 ther in a mortar and slowly add 280 c.c. distilled water. Filter, and to the filtrate add 20 c.c. 

 of absolute alcohol. Keep all of the above in glass-stoppered bottles. Logivood solutions ought 

 always to be filtered before they are used. 



I have found solutions prepared by any of the above methods to give excellent results. 

 They act very rapidly on nuclei, giving them a bright violet colour, softer and pleasanter to 

 the eye than the bright red stain of carmine. Many, however, prefer a solution which contains 



