SPECIAL METHODS. 



may be determined easily by a couple of trials. After wash- 

 ing, the preparations are transferred in the usual way to 

 Canada balsam. 



By the use of this method I have obtained a very good 

 staining of the nuclear crystalloids in both free hand and 

 microtome sections. They are always deeply stained, even 

 if all the other constituents of the nuclei, even the nucleoli^ 

 have been decolorized long before. 



c. The Acid-fuchsin-Potassium-bichromate Method. 



347- The third method, which may perhaps be briefly 

 called the "acid fuchsin method C," agrees almost complete- 

 ly with Altmann's method ( 345) in that here also the 

 microtome sections are warmed with a concentrated solution, 

 of acid fuchsin. But for washing a warmed solution of 

 potassium bichromate is used instead of picric acid, and the 

 result depends neither on the concentration of the solution 

 nor on the maintenance of a definite temperature. I used 

 mostly a concentrated aqueous solution of the salt heated in. 

 the paraffine oven to 50 or 60 C, but even a boiling solution 

 may be used. When the preparations are sufficiently washed^ 

 which can usually be readily recognized after a little practice,, 

 but may be determined by a few trials, the potassium bichro- 

 mate is quickly washed with water and then the preparation 

 is transferred to balsam in the usual way. 



By the use of this method I obtained always very clear 

 staining of the nuclear crystalloids. These remained still 

 deeply stained when the color had long been washed out of 

 the nucleolus. 



d. Double Staining with Acid Fuchsin and Haematoxylin. 



348. This method may be used in very different ways. 

 But I have generally found it best to first stain the objects 

 in mass with Delafield's haematoxylin ( 314), and then to 

 stain microtome sections cut from them with acid fuchsin by 

 the method B ( 346). Then, in one and the same nucleus 

 may be seen the deep red-colored crystalloids beside the 

 deep blue-violet nucleolus, within the violet nuclear frame- 



