a DR. G. THIN. 



iippev stratum of the liquid. The heat evolved by the solu- 

 tion of the potash should raise the thermometer above 120° 

 Fahr. "When the temperature falls to 107° Fahr. pieces of 

 a cornea are put in one after the other until the temperature 

 falls to 105°. From 107° to 105° is the most favorable 

 temperature. An ox cornea may be cut into four or five 

 portions and allowed to remain in the aqueous humour, 

 which should be saved for the purpose until the solution is 

 ready. Before putting them into the solution the excess of 

 aqueous humour is removed by bringing the portion into 

 momentary contact Avith the surface of a dry glass slip. 

 After being a few minutes in the solution the jDortions of 

 cornea are ready for examination. The froth should be 

 removed from the surface of the fluid by a small watch-glass, 

 and a clear drop removed by a glass rod to a glass slip 

 in which a small fragment of one of the pieces is broken up 

 by needles and examined. If the above precautions are 

 carefully observed, it is rare that at least one of the portions 

 is not found to consist of a multitude of the cells described 

 by the author. A solution previously made and heated over 

 a flame has not proved so successful as when the heat pro- 

 duced by the solution of the potash is employed. Fifteen 

 grammes is the smallest quantity that can be relied on as 

 invariably producing sufEcient heat. Of course any larger 

 quantity treated with an equal weight of water will be as 

 successful. Ten grammes sometimes, but not invariably, 

 produce sufficient heat. It is necessary that the caustic 

 potash be pure and dry. 



A cornea successfully treated should show nothing but the 

 cells. If any other substance of any kind Avhatever, formed 

 or amorphous, is seen, the oj)eration has been only partially 

 successful. Partial success, in which a greater or less num- 

 ber of cells are seen mixed with other substances, is very 

 common. When a perfectly successful cornea has been ob- 

 tained it may be kept some time in the solution in a Avell- 

 stoppered bottle. The smallest particle from any part of it 

 can then be used for demonstration or study when con- 

 venient. 



On all other tissues except the cornea the operator must at 

 present be prepared to encounter one failure after another, 

 but by persevering not only will all the results be obtained 

 Avhich have been previously described by the author as 

 demonstrable in connective tissue, nerve, and muscle, and 

 those now to be described in cartilage, but probably many 

 others whose discovery awaits a diligent application of the 

 process. 



