246 THE MICROSCOPE 



and syrup, but surrounded ^Yhen frozen with gum only. This 

 combination prevents the sections curUng up, or spHntering, from 

 being too hard frozen. Should the freezing have been carried too 

 far, the operator must wait a few seconds. It should cut like 

 cheese with the plane-iron. 



Embedding in Egg Mass (Prof. Calberla). — The whites of 

 several eggs are carefully separated from the yolks, and then the 

 fibrous portion known as the chalazeai is removed, and the rest 

 cut up with scissors. Fifteen parts of the white are now vigorously 

 shaken with one part of a lo per cent, solution of carbonate of 

 sodium. The yolk is now added, and the shaking repeated, and 

 the subsequent filtering removes the bubbles and fragments of 

 chalazeoe, etc. A small paper tray is filled with the resulting 

 fluid, and immersed in alcohol, which by abstraction of the water 

 coagulates the albumen, forming a solid block for embedding. One 

 of these blocks is taken and washed in water to remove the 

 alcohol, and then dried slightly with blotting paper. Scoop out a 

 small cavity, the surfaces of which are wet with the fluid egg. The 

 object is likewise deprived of alcohol by water, and is then jjlaced 

 in any desired position in the hollow. Now, a drojj of alcohol 

 will fasten it firmly by coagulation of the fresh egg. The block 

 is now washed again, and the fluid egg is poured over to cover 

 the object. To confine this egg it is best to place the object and 

 hardened mass in a box, and then pour in fluid egg. The box 

 and contents are then placed in a vessel, and exposed to alcohol 

 steam until the new portion of egg is coagulated. Various plans 

 for thus steaming have been devised. The simplest method is to 

 employ a fruit jar, in the bottom of which a little alcohol is poured. 

 The box is placed in the jar, and the opening closed with a glass 

 funnel. The whole is now heated in a water bath for from thirty 

 to forty minutes, care being taken the alcohol does not boil. The 

 mass is then removed and placed in alcohol, which should be 

 changed once or twice in the first twenty-four hours. It may 

 then be cut at any time, or the cutting may be suspended, and the 

 object kept indefinitely by immersion in alcohol. The object to 

 be cut should be stained before embedding, but the sections need 

 not be freed from the mass before mounting, as the coagulated egg 



