This method is valuable for rapid diagnostic work, but sections cannot often be cut sufficiently thin to allow a careful examination of the details.

The piece of tissue used should not be more than 4 mm. high and it must be free from all traces of alcohol. The alcohol is removed by placing the specimen in a large amount of water that is of a temperature of about 300 C.

The specimen is placed on the metal stand and a spray of ether or of carbonic acid gas is directed against the under side. The tissue is held in place by lightly pressing upon it with some flat piece of wood, as the handle of a small scalpel. Care must be taken not to freeze the tissue too hard or it will be so brittle as to break or show irregular streaks. The cut sections should be placed in 80 per cent, alcohol, as they will unroll better than if put directly into water.

The freezing method is particularly well adapted for tissues that have been hardened in Müller's fluid, as there is no change in the finer characteristics. Formalin is very useful, as it permits very good sections to be made and is employed especially in the rapid diagnosis of tumors.

A rapid method is as follows:

1. Take a small portion of the tissue that has been removed at the operation and place immediately in a 10 per cent, solution of formalin for about two minutes.

2. Freeze; put the sections into water to flatten.

3. Stain in lithium carmin two to three minutes.

4. Blot stain and mount in glycerin.