PROCEDURES FOR ALDEHYDES 87 



Voigt found, that acetal aldehyde in tissues is rather readily 

 broken down to free aldehyde by mercury solutions. It is prob- 

 able that mercury and other heavy metals can sometimes acceler- 

 ate oxidation processes, so that when mercury is used an arte- 

 fact is introduced, owing to oxidation of substances in tissues 

 which would not otherwise give an aldehyde reaction. This diffi- 

 culty is not encountered if fixatives and reagents devoid of mer- 

 cury are used, as in the procedure described above. 



The situation has also been somewhat complicated by the claim 

 of Dempsey, Bunting, and Wislocki that a-hydroxy-£-keto- 

 steroids may also be oxidised by cold aqueous mercuric solution 

 with the formation of aldehydes. This is very unlikely to occur. 

 Boscott, Mandl, Danielli, and Shoppee showed that when pure 

 deoxycorticosterone is treated with aqueous mercuric chloride 

 there is no indication of oxidation of the steroid. Deoxycorticos- 

 terone is a typical a, /^-hydroxy ketone. We may, therefore, say 

 with confidence that typical a,/?-hydroxy steroids will not be oxi- 

 dized in the manner postulated by Dempsey et al. There re- 

 mains, of course, the possibility that there may be some very 

 atypical hydroxyketones which would react with cold aqueous 

 mercuric chloride. However, if the procedure given above (pp. 

 85 and 86) is carried through there is no danger of complication 

 from such atypical compounds. It must, however, be empha- 

 sized that the claim that hydroxyketosteroids have been demon- 

 strated in tissues such as the adrenal gland, by the use of mer- 

 cury solutions as an oxidising agent, must be discounted until 

 the presence of atypical substances is in fact demonstrated by 

 orthodox chemical means. 



It should perhaps again be emphasized that one of the most 

 important control experiments in the study of aldehydes is to 

 carry a sample of tissue through the various steps of fixation 

 etc., under anaerobic conditions,, to eliminate the formation of 

 aldehydes, or substances which may react like aldehydes, by at- 

 mospheric oxidation of tissue components. Cain, following the 

 observations of Gomori and other workers, has quite correctly 

 drawn attention to the danger of encountering artefacts due to 

 atmospheric oxidation. But the procedures suggested by Cain 

 do not offer any satisfactory means of eliminating both this 

 and other artefacts. The procedure recommended above on the 



