150 Invertebrate Zoology. 



E. 



METHODS OF KILLING, FIXING, AND HARDENING. 1 



UNLESS animals or tissues are killed by some one of the 

 recognized agents, they will not give the best histological 

 results and the organs themselves will be often distorted and 

 unnatural. The killing agents that are more ordinarily used 

 are the following : Hot water (80 C.), weak alcohol, corro- 

 sive sublimate in hot or cold saturate solution, acetic acid, 

 Kleinenberg's picro-sulphuric acid, Perenyi's fluid, and the 

 varying chromic solutions. 



While the above reagents may be successfully used with 

 many animals, there are nevertheless many organisms that 

 violently contract on coming in contact with them. Such 

 organisms must first be rendered insensible by being anaesthe- 

 tized and then plunged into the killing agent. 



Chloral hydrate, weak alcohol, cocaine, chloroform, hydro- 

 xylamine, etc., have been used as anaesthetizing agents. 



Objects that have been killed by the use of many of the 

 above-mentioned agents are still soft and flabby and would, 

 if allowed to remain for any considerable length of time, 

 disintegrate. Several so-called " fixing " and " hardening 

 agents " have been adopted which are also frequently the 

 same as are adopted for killing. Such are corrosive subli- 

 mate, picro-sulphuric acid, Perenyi's fluid, and the chromic 

 solutions. Alcohol, used in regularly increasing grades of 



methods of killing, fixing, hardening, preserving, staining, etc., 

 are only given in the briefest possible way. It is taken for granted 

 that the students have at hand either an instructor or the admirable 

 text-books of microscopical technique which have been written by 

 Dr. C. 0. Whitman and A. B. Lee. 



