ZOOLOdY AND BOTANY, MICROSCOPY, ETC. 



821 



In using the apparatus, first heat the water-bath in which E is 

 placed to a temperature of 60° C, then put the bowls containing the 

 melted paraffin and the preparations to be imbedded into E and turn 

 on the water. The two thermometers Th and Th^ record the tem- 

 perature in W and in the bowl P. The spirit- or gas-lamp g should 

 be regulated so that the paraffin does not harden. When the 

 mercury is at the highest point and no more air-bubbles form on the 

 preparation, then the process is finished, and the air may be allowed 

 to enter through K. Before this is done, however, the cock on the 

 vessel E can be closed, so as to leave the preparation still longer in 



the vacuum. The cock can then be carefully opened and the air 

 allowed to enter. The small bent tube is for the purpose of pre- 

 venting the scattering of the paraffin by the entrance of the air. 

 Finally the object is taken out and put in a little box filled with 

 liquid paraffin. With sufficient pressure (700-720 mm. Hg) every 

 preparation, be it ever so difficult, provided that it is not too large, 

 will be penetrated by the paraffin in about twenty minutes, so that a 

 longer stay in tlic vacuum is only excei)tionally necessary. 



Preparations may bo left imbedded in this way for weeks in the 

 open air with unprotected cut surfaces without their undergoing any 



