Note on the Comparative Effects on Tissues of 

 Isotonic Saline and Distilled Water when 

 used as Solvents for Mercuric Chloride and 

 Pormol in Histological Fixation. 



By 

 H. M. Carleton, 



Lecturer in Histology, University of Oxford. 

 (From the Department of Physiology. ) 



Introductory. 



Should a simple fixative such as mercuric chloride or formol 

 be dissolved in normal (i. e. isotonic) saline or in water ? 

 Curiously enough, observations are lacking on this simple but 

 fundamental point. 



Gustav Mann (6) states that formol should be diluted with 

 isotonic saline ' because watery solutions cause such tissues as 

 blood corpuscles and the central nervous system to swell up 

 in whatever strength formol may be used '. That, moreover, 

 is the only reference based (apparently) on actual observation 

 which has come to my notice. 



Most authorities on microscopical technique (Langeron, 3 ; 

 Mallory and Wright, 5) advise that solutions of mercuric 

 chloride and formol be prepared in distilled water, while Lee (4) 

 advocates the dilution of formol with tap water, the salts in 

 this tending to neutralize the free formic acid always formed 

 after formol has been kept for any length of time. Finally, 

 among practising histologists and pathologists there does not 

 seem to be any consensus of opinion on the subject. Some 

 consider that it is immaterial whether mercuric chloride or 

 formol are dissolved in saline or water ; others hold that it is 

 ' safer ' to make up these substances in saline. 



The aim of these observations was to note the tissue-changes 



