94 



BACTERIOLOGY. 



pleted, in a mixture of ether and alcohol for an hour or more. 

 They are then transferred to a solution of celloidin in equal parts 

 of ether and alcohol, and left there, usually for several hours. 



The piece of tissue is then placed in a glass capsule, and some 

 of the celloidin solution poured over it. The capsule can be placed 



FIG. 27. SWIFT'S FREEZING MICROTOME. 



>x)dily in 60 to 80 per cent, alcohol, and left until the following 

 morning. The celloidin will then be of the consistency of wax. 

 The piece of tissue is next cut out, and after trimming off superfluous 

 celloidin is put in water until it sinks. It is then transferred to 

 gum, and frozen and cut with a freezing microtome. 



For cutting with Jung's microtome, the tissues are embedded 



