Method XI 73 



sections separately. When all are cleared, again place the dishes 

 in series and begin to mount, arranging the sections on the slide 

 in the order of the dishes, taking the first section from the first 

 dish, the second from the second dish, and so on, around and 

 back again, till all the sections have been mounted on slides which 

 are also numbered in series. 



APPLICATION OF THE WEIGERT METHOD TO MATERIAL PRESERVED IN 



FORMALIN. 



Material fixed and preserved in 10 per cent, formalin as in 

 Method X, I, p. 63, may be stained by the Weigert method 

 with fairly good results and with a procedure requiring less time 

 than the regular method. The preparations are sometimes not 

 so brilliant, however, as by the regular process. 



Remove such pieces from the formalin as are desired and 

 place them in 8-10 volumes of Miiller's fluid (A). In an incu- 

 bator or thermostat, expose the vessel to a temperature of 

 about 40° C for 4-8 days, changing the fluid daily for the first 

 3 or 4 days. The Miiller's fluid ifi this case serves as a mordant 

 by virtue of the potassium bichromate in it. A J^ per cent, 

 solution of chromic acid may be used, but, exposed to the heat, 

 this breaks down more readily than the Miiller's fluid. A 3.5 per 

 cent, solution of potassium bichromate will give better results 

 than chromic acid, but the Miiller's fluid by some virtue of 

 its formula is better than either. The method depends upon the 

 formation in the substance of the medullary sheath of a so-called 

 lake between the hsematoxylin and the chrome salt. 



After mordanting in the Miiller's fluid, wash and proceed to 

 imbed in celloidin, and further treat as before, beginning at step 

 2, p. 70. 



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