—145— 

 paraffin to the toluol or xylol containing the tissue to be 

 embedded ; the dish or bottle containing said tissue can at 

 this time he placed in the warm oven. In this wa}'' the 

 change from the toluol or xylol to the melted soft paraffin 

 can be made very gradual, and there will be less danger of 

 causing any shrinkage in the tissue. 



(4) From the soft paraffin, the tissues are transferred 

 to melted hard partfffin, which is usually a mixture of equal 

 parts of soft paraffin and a paraffin with a melting point of 

 about 52° to 55° C, and answers very well for ordinary 

 room or laboratory temperature. During the summer 

 months, it may be necessary to use two parts of the paraf- 

 fin with 55^ C. melting point, and only one of the soft, and 

 in very warm weather even less of the soft. 



In very warm weather the author has often used the 

 following mixture with success : 



Soft paraffin ... 1 part by weight. 



Hard paraffin ... 4 parts " " 

 Spermaceti ... 1 part " " 



In the hard paraffin the tissues remain from 2 to 24 

 hours, of course in the warm oven. It is essential that the 

 melted paraffins while in use for embedding should be at 



_ c 



I 





5^ 



,1^-:^ ^^jx^. 



A. 



'.[f 



Fig. I. Simple paraflBn bath; A, copper plate; B, paraffin tray; C, 

 loop of Alter paper; D, area of melted paraffla; E, area of uiimelted paraffin; 

 F, tripod; G, flame. 



a constant temperature ; this can easily be done when a 

 water-bath with temperature regulator, such as is found in 

 most laboratories, is at hand. A very simple apparatus, 

 and one that meets the requirements quite well, is shown 



10 



