1052 SUMMARY OF CURRENT RESEARCHES RELATING TO 



they arc allowed to lie for forty-eight hours. They arc then transferred 

 to a thin solution of cclloidiu in equal parts of ether and absolute 

 alcohol. Collodion being cheaper than cclloidin, and answering the same 

 purpose, is preferable. In this solution the piece of tissue remains for 

 at least three days, and is afterwards removed to a paper capsule filled 

 with cclloidin solution, and allowed to stand until a film forms on the 

 surface. The mass is then consolidated by immersion for twenty-four hours 

 in weak sjnrit, and the latter removed, in order that it may be sectioned 

 in a freezing microtome, by immersion fi>r 24 to 48 hours in Erlicki's 

 fluid (bichromate of potash 5; copper sulphate 1 ; water 200). 



The next step is to impregnate it with the last of the three following 

 mixtures (C): — 



A. Syrup (crystallized sugar 28*5 grm. to 31 ccm. water), 3 ccm. ; 

 mucilage (gum acacia, 57 grm. to 310 ccm. water), 5 ccm. ; water, 9 ccm. 



B. Solution A., 2 parts ; syrup as above, 1 part. 



C. Cupric sulphate, 1 grm. ; potassii bichrom., 5 grm. ; solution B, 

 200 ccm. 



It is kept in an air-tight bottle filled with this mixture for at least 

 three days at a temperature of 100° F. The microtome used by the 

 author is a Eutherfurd's freezer of large size, and the knife an ordinary 

 planing iron, such as is used by carpenters, and set in a wooden handle. 

 Before placing the piece of tissue in the well it should be wiped, in order 

 to remove the liquid in which it has been soaked. A quantity of 

 mucilage, only sufficient to cause the piece to adhere, is then poured into 

 the well, and in this the piece of tissue itself. The ice and salt in the 

 box must be frequently renewed in order to keep the temperature as low 

 as possible, and if the sections should adhere to the knife the mass is not 

 sufficiently frozen or the knife has become too warm. To keep the planing 

 iron cool it must be plunged in the freezing mixture after every four or 

 five sections. "When cut, the sections are removed at once to a dish filled 

 with Erlicki's fluid, in order to dissolve any mucilage that may be 

 adhering to it. No harm results if left herein for several days. The 

 section is next transferred to a dish filled with weak spirit to remove the 

 Erlicki's fluid. The spirit is to be changed once. A slide is now 

 covered with a thin film of collodion, in which the section is placed, in 

 the position it is intended to occupy, and when it has partially dried the 

 upper surface is covered with collodion. When thus fixed to the slide it 

 is transferred to absolute alcohol. If absolute or very strong alcohol be 

 not used the collodion may strip off the slide. After it has lain for a 

 few minutes in spirit it is ready for staining with Weigert's ha;matoxylin 

 (haematoxylin 1, absolute alcohol 10, carbonate of lithia 1, distilled 

 water 90 parts). The staining may be effected by leaving the prepara- 

 tion in a warm chamber at a body temperature for twelve hours or longer, 

 but a quarter of an hour suffices to stain the fibres, even without the aid 

 of the warm chamber, if the brain has been hardened long enough and 

 the solution of hjematoxylin of proper quality. 



When the section and surrounding collodion are thoroughly blackened, 

 the slide is washed in a running stream of tap water. The slide is then 

 transferred to the ferridcyanide and borax decolorizer (borax 2, ferrid- 

 cyanide of potassium 2^, water 100 parts), wherein it remains until all 

 superfluous stain has been removed from the grey matter. When 

 thoroughly decolorized, the slide, with the collodion still adhering, is 

 transferred to running water for twenty-four hours, in order to thoroughly 



