Chapter VI: The Paraffin Method 55 



mized. Observe the following modifications of the general method 

 and prepare pieces of ovary which have been fixed in Gilson. 



1. Pass the object in the usual manner up through the series 

 of alcohols to absolute. It is sometimes necessary to use a more 

 closely graded series of alcohols if the object be very delicate. 



2. From the absolute alcohol, pass to a mixture of absolute 

 alcohol two-thirds and chloroform one-third ; gradually add more 

 chloroform until at the end of an hour the mixture is at least 

 two-thirds chloroform. 



3. Transfer to pure chloroform for 30 minutes. 



4. Add melted paraffin little by little during the course of an 

 hour or two (24 hours will do no harm), until the chloroform will 

 hold no more in solution. 



5. Transfer the object to pure melted paraffin in a small ves- 

 sel on the paraffin oven for 10 to 20 minutes, changing the par- 

 affin once. Imbed in the usual way. 



6. Cut the sections about 7 microns thick. Mount and stain 

 some in Delafield's hematoxylin and eosin, and others in iron- 

 hematoxylin and Bordeaux red, according to the directions 

 already given for these methods. 



NOTE. For very sensitive objects Schultz's dehydrating apparatus 

 (to be obtained from dealers) may be used. It consists of a tube within 

 a tube, each having the lower end covered by an animal membrane. The 

 tubes are suspended in the neck of a much larger bottle which contains 

 95 per cent, alcohol. The object is placed in the inner tube and both 

 tubes filled with water. When suspended in the alcohol, a very gradual 

 hardening or dehydration of the object takes place as the alcohol slowly 

 diffuses through the membrane. Sometimes it is necessary to use only 

 one tube, and in such a case the hardening proceeds more rapidly. 



MEMORANDA 



1. In Passing from One Liquid to Another, one corner of the slide-bear- 

 ing sections should first be touched by blotting paper to remove any 

 excess of the liquid last used. This is especially necessary in trans- 

 ferring from absolute alcohol to xylol, or from 95 per cent, to absolute 

 alcohol. 



2. Sections Once Placed in Turpentine or Xylol for the removal of par- 

 affin must never in any subsequent step be allowed to become dry. 

 Particular care must be taken to prevent sections from drying out after 

 removing them from xylol to mount in balsam because the xylol evapo- 

 rates rapidly. If the sections become dry the preparation is usually 

 rendered valueless. 



