MICROSCOPICAL EXAMINATION OF BACTERIA. 



95 



in paraffine or celloidin, and mounted on cork ; or, if firm enough, 

 they may be fixed upon cork without any embedding material at 

 all. Paraffine, dissolved in chloroform, will be found vei'y .service- 

 able as an embedding material. 



Corks ready cut for the clamp of the microtome are smeai'ed 

 over with the solution of celloidin. This can be applied with a 

 glass rod to the surface which is to receive the piece of tissue- 

 The corks are then set aside for the film of celloidin to harden. 

 In the case of lung, or degenerated broken-down tis.sue, the 

 specimen should be left for a much longer time than is found to 

 be sufficient for firmer structures. When ready, it is removed 

 from the celloidin solution with forceps and placed upon the pre- 



FiG. 28. — JL'^"G's Microtome. 



pared cork. Enough of the solution, which is of syrupy consistence, 

 is allowed to fall on the piece of tissue to cover it completely, and 

 the mounted specimen is placed in the alcohol to harden. The 

 specimen will be ready for cutting next day. 



The specimen may be more neatly embedded by fixing it with 

 a pin in a small paper tray, pouring the celloidin solution over it, 

 and then placing the tray in alcohol to harden the celloidin. The 

 embedded specimen is then fixed on a cork, which has been cut for 

 the clamp of the microtome. The celloidin in the section disappears 

 in the pi'ooess of clearing with clove-oil. 



In the case of specimens embedded in celloidin, or mounted 

 directl)' on a cork, the tissue, as well as the blade of the knife, should 

 be kept constantly bathed with alcohol, and the sections transferred 

 from the blade with a camel's-hair brush, and floated in alcohol. 



