23O THE CIRCULATORY SYSTEM. 



pink in color ; the nuclei, of blue color of varying intensity, eosinophile 

 granules red, neutrophile granules reddish-lilac, basophile granules dark 

 blue or almost black. 



The hemoglobin shows itself in the form of crystals. In certain 

 teleosts the crystals are formed in the blood-corpuscles around the nuclei 

 and often within a short time after death. In old alcoholic specimens, 

 hemoglobin crystals (blood crystals) are found in the vessels and were 

 first discovered here by Reichert in the blood of the guinea-pig. They 

 have been found in large quantities in the splenic blood of a sturgeon 

 which had been preserved for forty years in alcohol. The hemoglobin 

 crystals belong to the rhombic series of crystallographic classification. 

 The simplest method of demonstrating hemoglobin crystals is probably 

 the following : The blood is first defibrinated by whipping or agitating 

 with mercury, after which process sulphuric ether is added, drop by drop, 

 until the mixture has been made laky ; this change may be detected 

 macroscopically by the sudden change from an opaque to a dark, trans- 

 parent, cherry-red color. No red blood-cells should now be seen under 

 the microscope. The preparation is placed on ice for from twelve to 

 twenty-four hours after which a drop of the blood is placed on a slide. 

 In half an hour it will be seen that the margin of the drop has begun to 

 dry. A cover-slip is now applied and, after a few minutes, numerous 

 crystals are seen to form at the margin of the drop, a process which may 

 be followed under the microscope. Large hemoglobin crystals are ob- 

 tained by Gscheidtlen as follows : Defibrinated blood is placed in a 

 glass tube, which is then hermetically sealed. The blood is now sub- 

 jected to a temperature of about 40 C. for two or three days ; if 

 then the glass be broken and the blood poured into a flat dish, large 

 hemoglobin crystals are immediately formed. Crystals also appear if a 

 drop of laky blood be placed in a thick solution of Canada balsam in 

 chloroform and covered with a cover-slip. 



Hemin crystals (Teichmann's crystals ; hemin is hematin-chlorid) 

 in the shape of rhombic plates are very easily obtained from the blood. 

 A drop of the latter is placed on a slide and .carefully mixed with a small 

 drop of normal salt solution. This is then carefully warmed until the 

 fluid evaporates and leaves a reddish-brown residue, after which a cover- 

 glass is applied and glacial acetic acid added until the space between 

 slide and cover-glass is filled. The preparation is now heated until the 

 acetic acid boils. As soon as the latter evaporates, Canada balsam may 

 be brought under the cover-glass, thus producing a permanent specimen. 

 When fluids or stains suspected of containing blood are to be examined, 

 the hemin crystals become of the utmost importance, as their demonstra- 

 tion is then a positive indication of the presence of blood. Fluids are 

 evaporated and treated with glacial acetic acid as above directed. Sus- 

 pected blood stains on cloth are treated as follows : Small pieces are cut 

 from the cloth in the region of the stain, soaked in normal salt solution, 

 and the resulting fluid treated as above. If the stain is on wood or other 

 solid object, the stain is scraped off and dissolved in normal salt and 

 then tested for hemin crystals. Hemin crystals are almost or entirely 

 insoluble in water, alcohol, ether, ammonia, glacial acetic acid, dilute 

 sulphuric acid, and nitric acid. They are, however, soluble in potassium 

 hydrate. 



A third form of crystals occasionally found in the blood and fre- 

 quently in the corpora lutea and, under pathologic conditions, also in apo- 



