398 



Medico-Legal 



The detection of blood in the presence of lime, mortar, and earth. 



The wide distribution of these substances rendered it necessary to 

 investigate their action (ni blood, since in medico-legal practice it might 

 often be necessary to test blood dried on, or mixed with, these materials. 



Solutions of earthy salts, mortar, and lime of various strengths 

 were made in salt solution and tested qualitatively with various 

 antisera to determine their action on serum. These actions vary to 

 some extent with the quantity of serum added. In the following table 

 the quantity added was one drop, since this was the unit chosen for 

 qualitative experiments. 



Dilutiotis 



Saturated fSOmins 

 solution* (24 hrs. 



1 : 10 



1 : 100 



1 : 1000 



1 : 10,000 





3. sa^ 



1 :25 



+ 



* Where saturated solutions are mentioned the dilutions are 1 : 10 etc. of these, 

 signs used here are described on p. 338. 



Tlie 



The addition of serum to strong solutions of lime resulted in a 

 general clouding, which later gave place to a dense cloud below, which 

 would be hard to distinguish from a positive reaction. Mortar gave rise 

 to a similar but smaller clouding. Calcium chloride and sodium and 

 calcium phosphates caused cloudings in very strong solutions only. 

 The actions of caustic soda and potash in certain solutions are very 

 marked, and are referred to on pp. 83, 85. They are briefly mentioned 

 here owing to their presence in earth. 



At this point it should also be noted that strong lime and calcium 

 solutions give rise on standing, even after filtration, to deposits of the 

 salt at the bottom of the tube and a filmy layer on the surface. 



It was found, however, that the difficulty in testing due to the 

 presence of lime in mortar, plaster, and earth, could generally be 



