2414 Journal of Applied Microscopy 



tinctness, the fibers being rendered less transparent than when mounted in 

 balsam ; rapidity of hardening, the cover-glass being firmly fixed within fifteen 

 minutes after attaching. 



The great tendency to forrh air bubbles would seem to make the method 

 objectionable, but where the object is not so much to produce ideally perfect 

 mounts, as to produce them rapidly, this matter is not of much importance, espe- 

 cially as by practice and care but few bubbles of consequence will be found in 

 the preparation. Charles E. M. Fischer. 



Textile Laboratory, Western Electric Co. 



A Rapid Method for Hardening and Embedding Tissues. 



Tissues can be readily hardened and embedded for cutting into sections in 

 a hot solution of agar-agar containing formalin. The proportions of the mixture 

 which have so far yielded the best results are 9 parts of a 5 per cent, aqueous 

 solution of agar-agar to 1 part formalin. This mixture can be prepared before- 

 hand and kept indefinitely in an air tight vessel. The agar-agar should be 

 boiled for several hours, and after the addition of the formalin allowed to clear 

 by sedimentation. The bits of tissue to be embedded are placed in a wide test 

 tube or wide mouth vial containing the mixture previously melted. This is kept 

 at 65 to 70°C. for an hour or longer, and the tissues are ready to be blocked. 

 After attaching to blocks, they are placed in strong or absolute alcohol for an 

 hour or two and can then be cut. It is important not to use dilute alcohol. 

 The tissues are stuck to the blocks by means of the agar-agar itself, and adhere 

 as soon as the agar becomes cold. No previous hardening of the tissues is at 

 all necessary ; fresh tissues can be placed at once into the hot agar-agar forma- 

 lin mixture; in fact, fresh tissue is more desirable than that which has been 

 previously hardened, though these can also be readily embedded by this method. 

 But the main advantage of the method, aside from its convenience and simplicity, 

 is the fact that the cells of the tissues are not at all contracted or shrunken, and 

 the ordinary methods of hardening do have this effect more or less. With sec- 

 tions prepared from fresh tissues by this method the cell-protoplasm fills out the 

 membrane fully, and the granules of the protoplasm, the nuclei and the cell con- 

 tours are remarkably distinct. The whole process, hardening, embedding and 

 cutting, does not occupy more than three or four hours, where the tissues are 

 not larger than about 1 cm. in diameter. 

 Marion Sims College of Medicine. B. Meade BoltON and D. L. HARRIS. 



