and Laboratory Methods. 2451 



Worcester's Formol-Sublimate Fixing Fluids. 



The killing and fixing fluids here described have been in use in the Zoolog- 

 ical Laboratory of the University of Michigan for a number of years. They 

 have proven so satisfactory for certain purposes that it has seemed desirable to 

 give other workers the benefit of the formulae. The fluids were discovered and 

 first used by Prof. Dean C. Worcester during the time when he was a member of the 

 staff of this laboratory. He used them with very satisfactory results in the 

 investigation on which be was then engaged, and had intended to publish the 

 formulae along with the general results of the investigation. For various reasons 

 it has not been possible to publish the results of this work, and, with the approval 

 of Professor Reighard, the formulae of two of the most important and useful of 

 Professor Worcester's killing fluids are here published. 



The fluids are essentially combinations of formalin and corrosive sublimate 

 made in the following manner : 



Formula I — Formol Sublimate. 



To 10 per cent, formalin add sufficient corrosive sublimate to make a 

 saturated solution. 



Formula II — Formol-Sublimate-Acetic : 



Formol-Sublimate fluid (Formula I), - - - 9 parts 



Glacial Acetic acid, ------ 1 part 



Formula I is especially adapted to the killing and fixing of Protozoa. For 

 this purpose it is extremely satisfactory. Some years ago the writer made a 

 rather extensive series of tests to discover the best fixing agent for infusoria. 

 Nearly all the fluids which had ever been advocated for this purpose were tried, 

 and by far the best results were obtained with this formol sublimate combina- 

 tion of Worcester. The fluid fixes cytological details with great precision and 

 completeness, and at the same time it kills so quickly that it is possible to fix 

 such delicate infusoria as Paramecinm without producing any appreciable distor- 

 tion of the body as a whole. The importance of this will be appreciated by 

 anyone who may have tried to fix Protozoa without distortion by any of the 

 ordinary methods. 



Formula II is especially adapted to the fixation of teleost eggs, and of embry- 

 ological material in general. I have used it on amphibian eggs, and have found 

 that it does not produce coagulation and cloudiness in the gelatinous envelopes 

 if thoroughly washed out. 



Material should be fixed in these fluids about as with an aqueous solution 

 (saturated) of corrosive sublimate. Washing may be done in water or in 4 j)er 

 cent, formalin. Four per cent, formalin may be used for preservation, or the 

 material may be carried up the grade alcohols and preserved 70 per cent. 



It is believed that these fluids deserve to, and will, become standard cytolog- 

 ical reagents. Raymond Pearl. 

 Zoological Laboratory of University of Michigan. 



