LESSON II. 



STRUCTUEE OF BLOOD. 



A. Blood op Feoq or Nkwt. 



1. Having destroyed the brain and spinal cord of a 

 frog\ cut through the skin in the median ventral 

 line, cut transversely through the lower part 

 of the sternum just above the epigastric vein, 

 and expose the heart. Cut off the tip of the 

 ventricle ; with a glass rod transfer a small drop 

 of blood to a glass slide and place on it a cover- 

 slip. 



Examine it under the microscope with a low 

 magnifying power* and observe the numerous 

 corpuscles floating in the plasma. 

 Examine it with a high magnifying power'' and 

 observe the red corpuscles ; if a large drop of 



1 Op. Appendix. 



2 For oonvenienoe the term ' low power ' will be used throughout 

 for a combination of lenses which magnifies less than 100 diameters, 

 and the term ■ high power ' for a combination of lenses which mag- 

 nifies more than 300 diameters. In Zeiss' microscope, objective A 

 with ocular 2 magnifies 55 diameters, with ocular 3 it magnifies 75 

 diameters; objective D with ocular 3 magnifies 320 diameters, with 

 ocular 4 it magnifies 440 diameters. If the tube be drawn out th^ 



3—2 



