396 Medico-Legal 



The detection of blood-stains on leather 1 . 



Several observations have been made with various samples of 

 leather, which have been placed under a separate heading to more fully 

 bring into prominence their peculiarities. It was found that nearly all 

 gave acid reactions on solution. The degree of acidity, however, varied 

 greatly, chamois leather being alkaline, suede kid glove only slightly 

 acid, and the coarser leathers very decidedly acid. The addition of 

 a drop of serum to the acid solutions produced clouding, and even 

 coagulation with extracts of the coarser leathers. The latter also gave 

 rise, especially if shaken, to bulky deposits in the original solutions. 



Nearly all the solutions of leather could be neutralised and the 

 blood test satisfactorily employed. One class of leather was, however, 

 a marked exception, namely, thick polished yellow leather. Solutions 

 of this gave rise to extremely acid yellow fluids, whose colour deepened 

 on the addition of alkali. It was found impossible to obtain the 

 specific test for blood dried on it. At first it was thought possible that 

 the blood was destroyed by the acid after solution, and extracts were 

 made in alkaline salt solution to neutralise this effect. Even under 

 these conditions no positive results could be obtained. Up to the 

 present although many methods have been tried we have been unable 

 to devise one which gives satisfactory results, and are forced to conclude 

 that the mode of preparation of such leathers produces conditions which 

 destroy the blood in contact with them. Under favourable conditions, 

 when blood has been thickly deposited on the surface, it might, however, 

 be possible to scrape it off and obtain a positive reaction. In the 

 following table all solutions when necessary were neutralised, and 

 filtered, before the addition of anti-human serum. 



A series of experiments was also made to determine the effects of 

 boot-blacking and polish. Blood-stains blackened over were hard to 

 detect on the boot, but by neutralisation and filtration clear solutions 

 could be obtained, and yielded well-marked reactions. Polish also 

 made no difference to the test. 



Experiments with saline solutions of tannin show that it has a very 

 deleterious action on serum, rendering the application of the test when 

 it is present in large quantities impossible. Solutions of 1 in 20 to 



1 See also p. 79 et seq. regarding the effects of acids on bloods, and Plate and 

 explanation on p. 402. 



