BLOOD. 



With fresh preparations on a slide and covered with a cover 

 glass, try the effects of the following reagents: acetic acid, chloro- 

 form, ether. 



Place another specimen of denbrinated blood in a freezing mixt- 

 ure. 



III. MICROSCOPIC EXAMINATION OF THE BLOOD. 



Appliances. Microscope, with a substage condenser, a high dry 

 and an oil-immersion lens. A stage micrometer. An eyepiece mi- 

 crometer. Slides and cover slips. Staining reagents, consisting of 

 methylene blue (aqueous solution), eosin (sat. aqueous solution), 

 Wright's stain. 



The slides and cover slips used must be scrupulously clean. 

 With new slides, washing with soap and warm water, and then 

 rinsing in distilled water, are generally sufficient. The glasses 

 should then be wiped dry with a clean soft linen or cotton cloth. 

 Handling the surfaces of the slides or cover slips with the fingers 

 should be avoided, since the oil from the skin deposited in this way 

 is hard to remove and prevents an even spreading of the blood- 

 film. Before using the slides or cover slips, they should be gently 

 warmed for a moment in the flame of the alcohol lamp or Bunsen 

 burner in order to get rid of any water of condensation. 



i . In the manner described before, obtain a drop of blood from 

 the finger or ear. Touch the middle of a clean glass slide to the 

 drop so that a small portion adheres to the slide. Avoid touching 

 the skin of the ear with the slide. Gently place a clean cover slip 

 over the drop and allow the blood to spread out in a thin film be- 

 tween the slide and the cover glass without using any additional 

 pressure. 



Examine this fresh specimen under the microscope with the high 

 dry lens. Note the color and form of the red cells. Compare them 

 with the leucocytes in relative number and form. Are the red cells 

 nucleated? What is the appearance of the red cells in profile? 

 Do the red cells vary in size and form ? If so, to what may these 

 variations be attributed ? 



