XIV, 2. Eisen: Notes on fixation, stains, the alcobol method, etc. 2(>1 



be regulated under the microscope. The diflferentiation is checked 

 when the cells in mitosis possess a red cytoplasm and dark blue 

 chromosomes. Dehydrate with absolute alcohol, clear with perfectly 

 fresh, and unoxydised berganiot oil, always followed at once by xylol. 



Dividing cells are now stained as follows : Chromosomes deep 

 blue, spindle fibres deep red, cytoplasm paler pink. Arehosomes 

 and centrosomes are only indifferently differentiated, but the spindles 

 are intense and almost every fibre can be connted. 



II. Stain for 12 to 24 hours or more in a very weak Solution 

 of tbionin, a couple of droppers of the stronger stain in a Naples-jar 

 of water. Rinse in distilled water and differentiate as before with 

 the ruthenium mixtnre. Watch the process under the microscope. 

 Dehydrate and clear as before. The cells of the festes are now 

 found to be stained quite differently. All the chromosomes in the 

 dividing cells as well as in the resting cells are stained either red 

 or reddish-brown, according to the quality of the ruthenium mixtnre. 

 The spindle fibres are deep blue, while the cytoplasm is pale blue ; 

 archoplasm is light gray, and centrosomes dark gray or blue. Tbere 

 • is absolutely no diffuse staining and the chromosomes stand out 

 clearly and may be readily connted. Even when they sligbtly overlap 

 each other no diffusion is had, and there is no difficulty in distinguishing 

 one chromosome from the other. 



So far I have only used these two methods in staining Salaman- 

 der testes. The first method I have also used for staining the divid- 

 ing cells in the anthers of Romnea coulteri and Magnolia (iridium 

 lixation), with very much the same results. The method is most 

 excellent for tuberous fungi. 1 



Gum-thus. 



This excellent mounting medium was introduced here by me 

 some three years ago and I have used it exclusively ever since. 

 I widerstand that.it has previously been used as a mounting medium 



J ) After having used this method for several months I tind that the 

 differentiation remains permanent ; but that it is absolutely necessary to use 

 only fresh bergamot oil. If the oil is oxydised or suur it chang-es at once 

 the red color to gray or brown. For this reason I prefer to use xylol for 



cleaning ruthenium stained tissues. 



