SECTION-CUTTING BY THE FREEZING METHOD 163 



SECTION-CUTTING BY THE FREEZING METHOD 



Sections which are prepared by the freezing method are rarely 

 as thin as those prepared by one or other of the infiltration 

 processes, but are prepared very rapidly, and are often sufficient 

 for diagnostic purposes, where rapidity is the first consideration. 



The blocks of tissue must be hardened before being cut, any 

 of the above fluids being applicable ; where alcohol is used it 

 must be washed out in water, as it will not freeze. Where 

 more rapid work is required the best method is a modification of 

 the old boiling process, as revived by Mr. Strangeways. The 

 slices of tissue from which sections are to be cut are thrown at 

 once into boiling water, and allowed to boil vigorously for two or 



Fig. 39. — Cathcart's Microtome arranged for gutting Frozen Sections. 



three minutes ; the water must be actually boiling when the 

 tissues are added, and the bulk used should be large as compared 

 with the block. The tissues are then rapidly cooled by being 

 thrown into cold water, and are then ready for cutting. The 

 outer surface of the block should be rejected. 



This method of fixation leads to a little distortion of the tissues 

 and alters any blood which they may contain, but it is very good 

 for diagnosing tumours. It is invaluable in the post-mortem 

 room, and for diagnosis of the nature of a tumour during opera- 

 tion. In skilful hands a section may be cut, stained, mounted, 

 and a diagnosis made in ten minutes ; or if no process of fixation 



