32 



(§ 124) ; rinse in water and dry. Mount in balsam without clear- 

 ing (§ 109), {b~) with EhrliM s iriacid mixture (§ 125). 



In the first preparations the red corpuscles will be red or pink, 

 in the second yellow or orange. Compare with 42 as to shape and 



size. 



44. Blood-plates. Demonstration. The tip of the finger 



was carefully cleaned with 95% alcohol, the finger pricked, a drop of 

 \% osmic acid was placed over the puncture and the blood squeezed 

 out into the drop of osmic acid, which was transferred to a slide, 

 covered, and sealed with castor oil. 



Note the appearance and size of the blood-plates in comparison 

 with the red corpuscles. 



AMPHIBIAN BLOOD. 



45. Blood of Necturus. A Nectunis was pithed, the gills 

 cut, and the drops of blood caught in a vial of 1% osmic acid. It 

 was allowed to fix in this 1-2 hours, washed in water, changed sev- 

 eral times, washed in 67% alcohol, stained several hours in paracar- 

 mine (§ 86), washed in 82% alcohol, 95% alcohol, absolute alcohol, 

 xylene and xylene balsam. Cover a drop of the balsam containing 

 the corpuscles. 



Note the shape of the corpuscles, their nuclei, size as compared 

 with human blood and frog's blood (42, 46). 



46. Blood of frog. Prepared as was 45. Mount a drop of 

 the balsam containing the corpuscles. Compare with 42, 45. 



LAMPREY BLOOD. 



47. Place a drop of the blood of the lamprey upon the center 

 of a slide, apply a cover-glass, and seal with castor oil. 



Study carefully the form of the red corpuscles and compare with 

 human (mammalian) blood as to form and size. Do they arrange 

 themselves in rouleaux? Observe the occurrence of leucocytes, 

 their number and size. 



Carefully wipe away the castor oil, lift the cover a little, and 

 place under the edge a small drop of 2% acetic acid. What is the 

 eflfect ? Compare with the efiect of acetic acid upon human blood. 



What difierences are there between the red corpuscles of mam- 

 malia, amphibia, and the lamprey ? 



