HEMOGLOBIN CRYSTALS. 53 



in the stratum immediately under the cover-glass. 

 The main substance of the corpuscle is uniformly 

 stained of a deep yellow, but many contain groups 

 of mahogany-stained granules, and from others are 

 seen to exude after a time pellucid drops of varying 

 size, which become tinted of a mahogany or port- 

 wine color, and no doubt contain glycogen. 



Preparation 20. Crystals obtainable from the 

 Coloring Matter of Blood. The hemoglobin or 

 coloring matter of the blood may be obtained in 

 definite crystals, but the form of the crystals varies 

 in different animals. It is difficult to induce the 

 crystallization in human blood ; and to obtain the 

 crystals readily it is best to employ the blood of the 

 rat. 



A drop of this is mixed with an equal amount of 

 distilled water, covered, and observed under the 

 microscope. The water has the effect of extracting 

 the hemoglobin from the corpuscles; until this is 

 done no crystallization takes place. As the excess 

 of water begins to evaporate at the edges of the cover- 

 glass small needle-shaped crystals of hemoglobin 

 begin to appear, either singly or in bunches, which 

 become larger and larger until they may attain a 

 very considerable size. 



Preparation 21. Crystals may also be readily 

 obtained from guinea-pig's blood, either by the same 

 method or more readily perhaps in the following 

 way: 



The animal is decapitated, and the blood as it 

 flows from the divided vessels is vigorously stirred 

 with a small bundle of wire, to remove the fibrin. 

 A small quantity of the whipped blood is then 

 mixed with about one-third its volume of water, 

 and, a drop of chloroform being added, the mixture 

 is thoroughly shaken up for a minute or two. This 

 has the effect of discharging the hemaglobin from 

 the corpuscles into the surrounding fluid. A small 

 drop is now placed upon a slide and left exposed to 



5* 



