THE ORDINARY METHODS OF PREPARING TISSUES. 19 



learn much that is new about the finer structures of the brain 

 and the character of the corpuscular elements of the body, bub 

 as yet it has not reached our expectations. 



Hailes' s microtome. A very ingenious and excellent instru- 

 ment (Fig. 10) has been devised by Dr. William Hailes, Pro- 

 fessor of Histology and Pathological Anatomy at the Albany 

 Medical College. Objections to it will be mainly on the ground 

 of price. 



Dr. Hailes uses it as a simple instrument or as a freez- 

 ing microtome, arranged either for ice and salt, ether-spray, 

 rhigoline, etc. 



The employment of ice and salt (coarse) is preferred, be- 

 cause it costs but little and freezes the mass solidly and 

 quickly, and, if desired, 500 or 1,000 sections can be obtained 

 in a few moments, depending, of course, upon the rapidity 

 and skill of the operator. 



The time of freezing is about seven minutes, except in 

 very warm weather, when it requires a few moments longer. 



The instrument does not work quite so satisfactorily in very 

 warm weather, owing to the rapid melting at the surface of the 

 preparation. 



It is absolutely necessary that the mass should be frozen 

 solid, or the sections cannot be cut smoothly. 



An extra freezer may be employed, and while one specimen 

 is being cut the other is being frozen ; by exchanging cylinders 

 (they being interchangeable) no delay is- necessary. 



The art of cutting is readily acquired. Two hundred or 

 two hundred and fift}^ sections have been made in a minute, 

 and of a uniform thickness of TY Vo- f an inch. It is not 

 necessary to remove the sections from the knife each time, 

 but twenty or thirty may be permitted to collect upon the 

 blade. They lie curled or folded up upon the knife, and when 

 placed in water, straighten themselves out perfectly in the 

 course of a few hours. The knife employed is an ordinary 

 long knife from an amputating case. 



Perfectly fresh tissues may be cut without any previous 

 preparation, using ordinary mucilage (acacia) to freeze in, but 

 most specimens require special preparation. 



If preserved in Miiller's fluid, alcohol, etc., they require to 

 be washed thoroughly for several hours, and then, according 

 to the suggestion of Dr. David J. Hamilton, F.R.C.S., etc., of 



