The Microscope. 181 



The watch glass must now be caref ally heated, either in what chemists 

 call a "double drying jacket" (which is similar to the incubator 

 already described, except that it has no wood-work, and wire shelves 

 replace the drawers), or over a water bath, until the paraffine is 

 melted and the chloroform evaporated. This properly takes from 

 12 to 24 hours, and is done in order that all traces of alcohol and 

 chloroform may be driven off, and the embryo become thoroughly 

 permeated with the paraffine. The embryo is then arranged at one 

 end of a paper cell which has previously been partly filled with 

 melted paraffine and the latter allowed to cool, and covered with 

 warm paraffine. 



B. If it is desired to cut ribbon sections, the paraffine used 

 should be that having the lowest melting point. When this is cold, 

 it must be carefully cut away around the embryo, which is again 

 embedded in a paraffine having a higher melting point. The reason 

 for this will be explained under section cutting. 



Should the specimen float out of place during the embedding 

 process, it may be returned to any position desired by the point of a 

 hot needle. All instruments used at this time that come in contact 

 with the embryo should be kept warm by holding in the spirit-lamp 

 flame; otherwise the specimen will adhere to them and perhaps 

 become torn and ruined. 



Air bubbles which frequently collect about the specimen should 

 be displaced by a hot needle before the upper layer of paraffine has 

 become hardened. Specimens embedded in this way may be kept 

 almost indefinitely. 



EDITORIAL. 



MODERN METHODS OF EMBEDDING. 



I HE recent progress made in the study of histology, both ani- 

 mal and vegetable, is due principally to three factors, namely : 

 improved methods of embedding, new stains with greater powers for 

 differentiating tissue-elements, and more precise section cutters. To 

 no one of these, it seems to us, should more credit be allowed, than 

 to the methods of infiltraliion and embedding; and students of a 

 decade ago who depended upon elder pith or amyloid liver for hold- 

 ing the ordinary histological or pathological specimen for cutting, or, 

 where greater care seemed necessary, employed the gum-arabic solu- 

 tion, or the abominable wax and oil mixture, cannot but be struck 



