92 NORMAL HISTOLOGY. 



and a fragment of the remaining substance teased in 

 water on a slide and studied ; but the objects thus ob- 

 tained are not altogether satisfactory, since the relation 

 of the fibrillae to one another is disturbed and no light is 

 thrown on the way in which they are formed. For the 

 accomplishment of these ends, the following method may 

 be employed : a medium-sized drop of blood is received 

 on a slide and immediately covered ; after a few mo- 

 ments, when coagulation has occurred, the cover-glass 

 is gently raised with the forceps, and the blood-cells 

 washed out of the clot by allowing drops of water to fall 

 upon the inverted cover-glass from a pipette held a few 

 inches above the preparation. (If, in removing the 

 cover-glass, the clot adheres to the slide, the water is, of 

 course, to be applied here.) When no more color is seen 

 in the clot, a drop of the above solution of Fuchsin is 

 placed upon it, and it is again covered. The fibrin will be 

 seen in the form of minute inosculating filaments which 

 often radiate from the above-described blood placques. 



Blood Placques. These may be seen in the preparation 

 of fresh blood, if the drop is small and it has been spread 

 out thin. It is better to dilute the blood, as the red 

 cells are apt to obscure the view of them. For the 

 purpose of dilution a one-per-cent. solution of osmic acid 

 is used as follows : a drop of the solution is placed on 

 the finger and the skin punctured with a needle 

 through this ; the resulting drop of blood is then thor- 

 oughly mixed with the dilutant, transferred to a slide, 

 covered, and examined. The osmic acid being an ex- 

 cellent fixative agent, the form of both the blood-cells 

 and placques are well preserved. 



