1 1 2 Transactions of the [Sess. 



XVII.—ON THE GATHGART ETHER FREEZING MICROTOME. 



By Mr ALEXANDER ERAZER, M.A. 



{Exhibited in operation, with remarks, March 22, 1883.) 



The increasing attention which in recent years has been given to 

 investigations in which the microscope is used has led to the 

 invention of many instruments by means of which thin sections of 

 animal and vegetable tissues may be prepared for examination. 

 The construction of an instrument by means of which sections of 

 comparatively hard substances may be cut does not present special 

 difficulty, and need not be further alluded to. But the cutting of 

 thin sections of soft substances is a difficult matter, and one upon 

 which much ingenuity has been expended. The method now 

 almost universally adopted is that of freezing the tissue to be cut, 

 so that for the time being it is not a soft substance, but a hard 

 one. Freezing is effected in two ways, — first, by using a freezing 

 mixture, such as ice and salt ; and second, by the rapid evapora- 

 tion of ether. For most purposes, microtomes which effect freezing 

 by means of a freezing mixture are to be preferred ; but many 

 circumstances render the use of these instruments inconvenient, 

 and in some cases they are quite inapplicable. When a freezing 

 mixture is employed, ice and salt are the usual elements of the 

 freezing compound. Now salt may be carried to any part of the 

 world, and is procurable in most places ; but ice cannot, and even 

 in cities time and trouble are required to procure it, after which 

 the laborious process of reducing it to a finely divided condition 

 must be undertaken. Further objections are to be found to ice- 

 and-salt microtomes, in the facts that they are slow in action and 

 rather uncleanly. 



It is obvious that ether is not liable to the objections attending 

 the use of ice and salt. Ether may be carried anywhere, and can 

 be procured in most places, — while it is at once ready for use, and 

 is quite cleanly. The principal objection to the use of ether micro- 

 tomes has been, that they have hitherto been both expensive in first 

 cost and in after use. The cause of the expense of using ether 

 microtomes is due to the fact that ether is comparatively a costly 

 fluid. The instrument about to be described has been designed by 

 Dr Cathcart to overcome these objections. The first cost (15s.) is 

 inconsiderable, being less than half that of a well-made Ruther- 

 ford's instrument ; while the microtome has been so arranged as to 

 freeze with a very small quantity of ether. In most ether micro- 

 tomes hitherto devised, ether has been used not only to freeze the 



