Il] BLOOD CORPUSCLES OF FROG 13 



a frog is destroyed, and the wound plugged with cotton-wool. A 

 drop of curari is injected under the skin ; this paralyses the lymph 

 hearts, so that the lymph accumulates in the lymph sacs. The 

 frog is kept in a dish containing water about J- inch deep, for 

 half-a-day to a day. Lymph may be obtained from any of the 

 lymph sacs, but, if the frog has been placed in a normal position, 

 in especial quantity from the ventral sacs, beneath the skin of the 

 abdomen. Since the lymph clots quickly when withdrawn, not 

 more should be taken up in the pipette than is required at the 

 time. 



4. a. Place on a cover-slip a small drop of lymph, 

 with a needle take a little culture of a large bacillus 

 (e.g. b. filamentosus), and stir it into the drop. Examine 

 as in 3. White corpuscles will be seen to attach 

 themselves to the bacilli, some crawling over the bacilli, 

 others ingesting them. 



b. The white corpuscles which have ingested foreign particles 

 will be seen, if a drop of milk or if a drop of water containing hay 

 bacillus, or Indian ink, be injected into a lymph sac about an hour 

 before examining the lymph. 



5. Irrigation. Cut a triangular piece of blotting- 

 paper, cut away one of the angles and apply the cut 

 edge to the middle of one edge of the cover-slip ; place 

 a small drop of '1 p.c. acetic acid on the slide near the 

 opposite edge of the cover-slip, and lead it with a needle 

 to the edge taking care that the fluid does not run on 

 to the upper surface of the cover- slip. Note the changes 

 which take place as the acetic acid mixes with the 

 blood. 



a. In the colourless corpuscle, the cell sub- 

 stance becomes more transparent but shows some irre- 

 gular granules; a granular nucleus comes into view. 

 As a rule the nucleus is somewhat crescent-shaped in 



