35 



small leucocytes with a large rouud nucleus and scanty protoplasm, 

 (b) large lymphocytes , large leucocytes with a large, clear nucleus 

 and ratlier scanty protoplasm, (c) polymorphonuclear neutrophiles, 

 medium-sized leucocytes with irregular, horse-shoe shaped nucleus 

 or several nuclei, the protoplasm granular, and (a?) leucocytes with 

 the nucleus irregular or in two or more parts, protoplasm containing 

 large granules that stain intensely with eosin (or other acid staining 

 principle), hence they are called '"eosinophiles" . (c) will be most 

 abundant, (a) and (6) less abundant, (d) least abundant. It is 

 generally believed that (a), (*), (f), and {d) are stages in the 

 growth of a leucocyte from youth to old age. Consult 



FIBRIN. 



52. Upon a clean cover glass place a large drop of fresh human 

 blood and cover it with another cover glass, taking care that the 

 two covers are a little eccentric to each other. Place the two covers 

 so prepared in a moist chamber (on the table) for 15 minutes or 

 longer. Transfer the two covers to a slide, flood them with water 

 and carefully separate them. Wash the film side of each very care- 

 fully with water by means of a pipette to remove the red corpuscles. 

 Stain the film side with eosin or erythrosin for 5 minutes, drain off 

 the stain and dry without washing. When dry mount the better of 

 the two preparations upon a shellac ring film side down. 



Observe the network of the fibrin coagulum adherent to the 

 cover. 



BLOOD CRYSTALS. 



53. Hemoglobin. Place upon a slide a small drop of mam- 

 malian blood (rat, cat, or human) ; place beside it a small drop of a 

 10% aqueous solution of pyrogallic acid ; cover both drops with a 

 cover-glass and seal carefully with castor oil. L,abel the slide so 

 prepared with your name and place it upon the window sill. At the 

 second period {i. e., after one or two days), examine it for crystals 

 of hemoglobin. These will be found near the line where the drops 

 of blood and pyrogallic acid met. Observe their color, shape and 

 arrangement. 



54. Oxy-hemoglobin. Blood of Necturus. Demonstration. 

 A plentiful supply of Necturus blood was placed upon a slide, mixed 



