120 



PRACTICAL HISTOLOGY. 



[III. 



specimen as a permanent preparation. Numerous purple stained 

 threads of fibrin are seen stretching from colourless corpuscles, the 

 latter having their nuclei stained purple. 



Crystals from Blood. The haemoglobin of certain animals 

 crystallises very readily, e.g., rat, guinea-pig. 



9. Haemoglobin Crystals of Rat's Blood (H). Place a drop of 

 defibrinated rat's blood on a slide, add two drops of water, and mix, 

 Apply a cover-glass. After a few minutes, near the edge of the 

 cover-glass oblique rhombic crystals of haemoglobin will be found. 

 At first they are small, but they gradually become larger. They 

 may be single, or arranged in rosettes, or crossing each other 



(% 79)- 



10. Crystals from Guinea-Pig's Blood (H). To a drop of the 



FIG. 78. Fibrils of Fibrin 

 of Coagulated Blood. 



FIG. 80. Hicmo- 

 globiu Crystals 

 from Blood of 

 Guinea-Pit'. 



FIG. 79. Haemoglobin Crystals from 

 Rat's Blood, x 300. 



defibrinated blood add a drop of Canada balsam or clove-oil, mix, 

 and apply a cover-glass. It is perhaps better to place the balsam 

 or clove-oil on the slide first, then to place the drop of blood on 

 the top of the oil or balsam, and then to mix them ; very soon 

 (about 10 minutes) large red tetrahedral crystals are formed. 

 These crystals cannot be preserved for any length of time (fig. So). 



Sometimes very good crystals of haemoglobin from human blood 

 are obtained from leeches which have sucked blood some weeks 

 previously. 



11. Hsemin Crystals (H). Place a few particles of dried blood 

 on a slide, add a small crystal of common salt, and two drops of 

 glacial acetic acid. Cover. Heat over the flame of a spirit-lamp 

 until bubbles of gas are given off, i.e., until it boils. Allow it to 

 cool. Or mix fresh blood on a slide with a minute quantity of 2 per 



