132 THE AMERICAN MONTHLY [May, 



into the paper from its edges dissolves the gum-arabic, 

 and the block is thus detached from the glass. The film 

 of gum between the collodion and the paper is also dis- 

 solved, so that the paper can then be removed, leaving 

 the block of parafiin with the imbedded object. The ob- 

 ject thus lies close to the lower surface of the block, over 

 which is the delicate film of collodion and the imprint of 

 the grain of the paper. One face of the paraffin block, 

 which is a plane surface, thus bears a cast of the grain 

 of the paper, the lines of which have definite relations 

 to the axes of the imbedded object. It is now a simple 

 matter to orient the block in the microtome so that the 

 lines on the face of the block will have any position in 

 relation to the plane of section. A whole series of ob- 

 jects can thus be oriented on one strip of paper ; and 

 with a fine pen numbers referring to notes and drawings 

 can be marked on the collodion surface adjacent to each 

 object. These marks will appear on the face of the par- 

 affin block after imbedding. The film of collodion on the 

 face of«the block in no way interferes with making good 

 "ribbons," for, owing to the fact that the collodion was 

 much diluted, the film is so fine that it offers practically 

 no resistance to the knife in cutting, and does not endan- 

 ger the specimen. 



Although necessitating a rather long description, the 

 method is extremely simple. The chief advantages are : 



(1) the easy orientation of objects when filled with some 

 clearing medium, by which details are made more visible ; 



(2) the conspicuousness of the objects through all stages 

 of the process ; (3) the saving of time in being able to 

 imbed many objects at one operation ; and (4) the absence 

 of any necessity for haste. The method has been tested 

 by others with various objects, and always with success. 



Dr. Hauser. — A chair of Bacteriology is to be established at 

 Erlangen and Dr. Hauser will probably occupy it. 



