60 



tic lacunae and canalictdi of the bone tissue when cleared and ex- 

 amined under the microscope with a low'power lens. It also gives 

 off a little carbon dioxid on the addition of hydrochloric acid. 

 (Fig. 51.) 



DRIED BLOOD. 



This substance, when it occurs in feeds, appears to the naked 

 eye to be made up of irregular black lumps, small in size, which 



Figure 52 

 Fig. 52. Dried Blood. Hemin crystals. 



are rather hard to crush in dry condition. Its presence may be 

 confirmed by the so-called hematin test.^^^ This is made as 

 follows : — 



The material is placed on a slide with a little water to which 

 a small crystal of sodium chloride has been added; the solution 

 is then allowed to evaporate until nearly dry and a cover slip put 

 on. A few drops of glacial acetic acid are then introduced under 

 the slide and the whole heated on a radiator for three or four 

 minutes, adding acid from time to time ; — then the slide is removed 

 and slowly cooled. If sufficient care has been used small plate 

 crystals of the substance will be found on the slide. These in- 

 dicate the presence of blood. (Fig. 52.) 



3 U. S. Dept. Agr. Bur. of Chem., Bui. 108, p. 78. Figs 51 and 52 are reproduced from 

 this bulletin. 



