Il] THE BLOOD. U3 



ADDITIONAL EXERCISES. 



18. Migration of Colourless Corpuscles ( H ). Heat and draw out a glass 

 tube so as to form an excessively fine capillary tube. Pith a frog, expose its 

 heart, make a cut into the latter, and as the blood flows suck up blood into the 

 capillary tube. Seal the tube at both ends by holding it for a second or two 

 in a gas- flame. 



Place the tube on a slide in a drop of glycerine or clove-oil, rover it and 

 examine. 



( a -) (L) Observe that the blood-clot shrinks, squeezes out serum from the 

 clot, and by-and-by some of the colourless corpuscles migrate from or are 

 squee/ed out of the red clot into the serum, where they may be seen exhibiting 

 amreboid movements. This shows that the vitality of the white corpuscles is 

 not abolished bv the coagulation of the blood. 



19. Feeding White Corpuscles ( H ). Get some blood from the~heart of a 

 frog into a capillary pipette, as described in 18. Allow the blood to clot and 

 exude serum, which it does in about an hour. 



liiib up a little Indian -ink in a few drops of normal saline in a watch-glass 

 till a greyish fluid is obtained. Blow the contents of the capillary tube upon 

 a clean slide, remove the clot ; the serum contains numerous colourless cor- 

 puscles. Mix a little of the greyish Indian-ink fluid with the serum, put 

 a hair under the cover-glass, and seal up the latter with melted paraHin to 

 prevent evaporation. After a time, observe that the minute particles of 

 Indian-ink are seen included in the protoplasm of these cells. The cells throw 

 out processes which surround a particle, meet and coalesce, and thus the 

 particles come to be included in the corpuscle (Schcifer). 



20. Movements and Division of White Corpuscles. Ranvier 1 seals up the 

 preparation on the slide devised by him, this being done by paraffin wax. A 

 water immersion lens is placed on the microscope, and then the microscope 

 with the slide is placed in a glass vessel filled with water at the required 

 temperature. In this way the movements of the corpuscles, and, as I have 

 myself seen, even the division of leucocytes, can be readily studied. 



21. Glycogen in White Corpuscles (H). Irrigate a preparation of frog's 

 or newt's blood with I per cent, solution of iodine containing 2 grams of 

 potassic iodide. The red corpuscles are stained yellow, the white ones arc 

 killed ; many of them are also stained yellow, but' in some of them may be 

 seen mahogany-coloured granules of stained glycogen. 



22. Elder Pith Preparation (H). Into the dorsal sac of a pithed frog 

 introduce a small piece of elder pith soaked in normal saline, and leave it 

 there for twenty- four hours. Withdraw it, make a thin section, and examine 

 it in normal saline solution. 



(a. ) Observe the large polygonal cells of the elder pith crowded with lymph 

 corpuscles several varieties which have, in virtue of their amoeboid move- 

 ments, " wandered" into and permeated the cellular pith. 



The elder pith may be hardened in Flemming's fluid (p. 32), and after 

 thoroughly washing it, sections are made and mounted in Farrant's solution. 



23. Serous Fluids of Mammals. A small mammal, e.g., mouse, rabbit, is 

 killed by decapitation. Open its peritoneal cavity by means of a sharp red-hot 

 knife, i.e., by a therm o-cautery. This is to avoid any blood being shed into 

 the cavity. By means of a fine pipette withdraw some of the "lymph" or 

 " serosity." It will be found not to be clear like whey, but slightly opalescent. 



(a.) Corpuscles (H). Some are like ordinary lymph corpuscles, many are 

 ve'-y granular, and there are always red blood-corpuscles also present (llanvier). z 



1 Comptcs llendus, vol. 110, p. 686, 1890. 



2 Ibid. vol. 110, p. 768, 1890. 



H 



