LESSON III. 



BLOOD (Concluded). 



(a) Fibrin. 



Place a large drop of blood on the slide, allow it to clot par- 

 tially ; cover with a cover slip. Wash gently with a current of water 

 until nearly all the red blood cells have been washed out. Run a 

 few drops of a \% solution of methylene blue under the cover 

 glass. 



Examine with high power. Small glistening fibrillse 

 woven into a network will be seen ; these are fibrin filaments. 

 The nuclei of the white blood cells will be stained blue. 



(b) Teichmann's Crystals, Hsemin Crystals, Chlo- 



ride of Hsematin. 



Several weeks ago the blood of a mamin:il was allowed to flow 

 on a piece of cloth. Cut out a small piece of the cloth with a por- 

 tion of the blood-stain on it. Tease it on a slide in a few drops of 

 normal snlt, and set it aside until some of the stain soaks out into 

 the solution. In case the normal salt begins to evaporate add now 

 and then a drop of the solution in order to keep the teased fibres 

 well soaked. When some of the blood has been dissolved by the 

 salt solution, remove the cloth fibres, and set the slide away to evap- 

 orate. If care be taken not to t/ct the slide too hot, the evaporation 

 can be hastened by holding the slide over a gas flame. When the 

 evaporation has been completed, scrape what is left on the slide hit > 

 a small mass, and add one or t\vo drops of glacial acetic acid, cover 

 with a cover glass, and heat over a flame until bubbles form. Con- 

 tinue the heating till the acid has evaporated. Run a drop of water 

 under the cover glass, and examine for Teichmann's crystals. If 

 present, the cover glass may be removed, dried, and mounted oh 

 balsam. 



Study under high power. The crystals are seen in the 

 form of rhombic plates or rhombic rods of a brownish-red 

 color. 



(c) Teichmann's Cyrstals from Pigeon's Blood. 



Prepare as (b) of this lesson. 



