THE EFFECTS OF FORMALDEHYDE ON THE BRAIN 

 OF THE ALBINO RAT 



HELEN DEAN KING 



The Wistar Institute of Anatomy and Biology 



TEN CHARTS 



Although formaldehyde was discovered in 1863, it was not until 

 thirty years later that Blum ('93) and Hemiann ('93), working 

 independently, found that an aqueous solution of this substance 

 is an excellent medium for preserving and hardening various ani- 

 mal tissues. Owing to its many admirable properties and to its 

 relative cheapness, 'formalin' (a commercial 40 per cent solution 

 of formaldehyde) soon became extensively employed as a fixing 

 and preserving reagent for entire brains as well as for other large 

 pieces of tissue, being used either in a 5 to 15 per cent aqueous 

 solution or combined with other substances such as alcohol, alum 

 or salt. 



In an extensive series of experiments dealing with the effects 

 of various formalin solutions on the weight of the brains of man, 

 of sheep and of various other mammals, Hrdlicka ('06) showed 

 that the size of the brain, the age of the animal from which the 

 brain was taken and the strength of the solution used were all 

 factors that influenced the weight and volume changes in the 

 brain to a very considerable extent. Hrdlicka did not, however, 

 ascertain the relative importance of these various factors, nor 

 did he make any study of the histological effects produced in 

 the brain tissue by formaldehyde solutions. At the present time 

 formalin is commonly used in laboratories and museums as a 

 fixative and also as a preservative for the brains of man and of 

 other mammals. It has seemed worth while, therefore, to make 

 a careful study of the changes produced by this substance, act- 

 ing under different conditions, on a series of brains from animals 

 of known ages from birth to maturity. Experiments of this kind 



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