90 STUDENTS HISTOLOGY 



H^EMIN CRYSTALS 



Let a drop of blood dry on a slide. Add a few drops of glacial acetic acid, 

 and heat over a flame until bubbles appear. Dry and mount in balsam. Dark 

 brown rhombic prisms will be seen, which are crystals of hsemin, or the crystals 

 of Teichmann. They are proof of the presence of blood, but do not indicate 

 its source. They may be of importance in medico -legal cases. 



FIBRIN 



The delicate network of straight fibrin filaments is easily demonstrated by 

 the method recommended by Gage. A large drop of blood is placed on a slide, 

 and is covered with a cover-glass. The slide is laid on a piece of wet blotting 

 paper, and covered with a saucer to prevent evaporation. After half an hour 

 coagulation will have occurred. Draw a drop of water around the edge of the 

 coVer-glass, and float it carefully from the slide, endeavoring to keep the 

 coagulum of fibrin on the cover-glass. Wash carefully in water, stain in 

 hsematoxylin and eosin; dry; mount in balsam. (Gage recommends mounting 

 without balsam over a hard-rubber cell.) 



EFFECT OF REAGENTS 



Reagents produce characteristic changes in the blood-corpuscles. 

 A strong saline solution leads to the formation of projections on 



FIG. 65. BLOOD-CORPUSCLES OF FROG. (RANVIER.) 



the red corpuscles, known as crenation; if sufficiently concentrated, 

 the corpuscle becomes a shrunken, shapeless mass. Water causes 

 the red corpuscles to swell ; the haBmoglobin is finally dissolved 

 out, leaving the colorless, barely visible outline of the stroma called 



