104 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 

 .GUAIACUM AS A TEST FOR BLOOD-STAINS. 



The frequent occurrence of the necessity of identifying 

 blood-stains in medical legal cases has brought out the fact 

 that there is one good test, which answers the purpose suf- 

 ficiently, although, unfortunately, it does not enable us to 

 distinguish human blood from that of other animals ; the con- 

 stituent, haematine, upon which the reaction is based, being 

 identical in all blood, even in that of the common earth-worm, 

 as is proved by the spectroscopic appearances. To apply the 

 test, a drop of blood is placed, on a white surface of porcelain, 

 and a drop of simple tincture of guaiacum added. If then a 

 drop of the solution of peroxide of hydrogen be added, a blue 

 color will be developed. If the stain of blood be dry, moist- 

 en with glycerine, apply the tests, and press it with a piece 

 of white blotting paper; this will absorb the color. This ac- 

 tion depends on the oxidation of guaiacum in the presence 

 of the haBmatine. 1 A y January 19, 1872, 26. 



CHEMICAL COMPOSITION OF GASES IN THE SWIMMING 



BLADDERS OF FISHES. 



According to Schultze, the gases contained in the swim- 

 ming bladders of certain cyprinoid fishes consist of oxy- 

 gen, carbonic acid, and nitrogen in different proportions, the 

 amount of oxygen never exceeding that in the atmospheric 

 air, and carbonic acid, being always present. He concludes 

 from his experiments that in such fishes the swimming blad- 

 der contains the ordinary gases found in the expired air of 

 the lungs and gills. 21 A, March, 1872, 254. 



DISCRIMINATION OF BARLEY FROM WHEAT STARCH. 



The following method of discriminating barley starch from 

 that of rye or w 7 heat has been announced : The flour is placed 

 on a glass slide and moistened, with water, a covering of glass 

 is laid upon it, and a single drop of oil of vitriol added. If 

 now viewed with a magnifying power of 200 the starch grains 

 of wheat and rye are seen to dissolve in a uniform manner, 

 but the grains of barley starch, after losing their external 

 coat, break up into a number of polyhedrons before their so- 

 lution is completed. 21 A, April, 1872, 320. 



