120 OKGANISED FLUIDS. 



The observance of one precaution, at least, is necessary 

 for the successful exhibition of the microscopic characters of 

 blood stains. 



Thus, water should never be applied to them, nor indeed 

 any other fluid, the density of which is less than that of the 

 serum of the blood, for all such liquids will occasion the 

 discharge of the colouring matter of the blood corpuscles and 

 an alteration of their form ; thus the circular but flattened 

 corpuscles of the Mammalia will assume a globular shape, as 

 will also the elliptical blood discs of birds, fishes, and rep- 

 tiles, one of the greatest points of difference between the 

 blood corpuscles of the former and latter classes being 

 thereby effaced. 



Blood stains, therefore, should be moistened, previous to 

 examination, with some fluid, the density of which nearly 

 equals that of the liquor sanguinis ; and I have found the 

 albumen of the egg to preserve the form of the corpuscles 

 excellently well. 



Failing, however, in detecting the blood corpuscles, a 

 result scarcely to be anticipated, assistance may be derived 

 from a toxicological examination of the blood. 



The only tests peculiar to the blood are those which have 

 relation to the hocmatine. This principle it would, however, 

 be difficult to obtain from blood stains in sufficient quantity 

 for the purposes of copious chemical analysis. 



Nevertheless, corroborative evidence of the suspected cha- 

 racter of a stain might be obtained by its general chemical 

 analysis, and which should be treated as follows. 



The stain should first be moistened with cold distilled 

 water, as much of the matter of it should then be removed as 

 possible, and placed in a test tube with an additional quantity 

 of water. This being agitated, the colouring material, if the 

 stain be a blood stain, will be dissolved by the water, imparting 

 to it a pinkish colour, while, provided the blood flowed from 

 the body during life, or at all events within a few minutes of 

 decease, suspended in the liquid, will be seen shreds of fibrin. 



This solution, when heated to near the boiling point, will 

 become turbid, and deposit flakes of albumen. 



