189^.] MICROSCOPICAL JOURNAL. 247 



iodine solution to run under. This stains tlie lymphatic 

 globules mahogany brown. . . . 



Globules examined in the serum appear uniformly 

 granular and the nuclei are invisible. Run under a little 

 water ; the protoplasm swells, becomes transparent, the 

 nuclei appear and exhibit their whimsical forms. 



To examine the inigrating ability of the lohite corpuscles. 

 — . . . .Insert a small cylinder of elder pith into the dor- 

 sal sac of a frog. Let it remain 24 hours ; expose to the 

 vapor of osmic acid. Cut longitudinal sections, and ex- 

 amine in water. To make the preparation permanent, 

 stain in alum carmine and mount in glycerine. Only the 

 cells in the superficial layers show amoeboid expansions, 

 those in the central parts are rounded and have under- 

 gone fatty degeneration ; these are dead elements, anal- 

 gous to pus globules. This experiment proves that oxy- 

 gen is necessary for the amoeboid activity of lymphatic 

 cells ; where this gas is absent (in the centre of the pith 

 stick), the amoeboid activity ceases, and the cell dies. 



To observe the absorption of granules. — . . . .Rub up in 

 a little water some vermillion or an aniline blue insolu- 

 ble in water, until the coloring matter is an impalpable 

 powder. Inject into a frog's dorsal sac 1 c. c. of water 

 to which has been added a small quantity of this mix- 

 ture. In a few hours the lymph cells of the dorsal sac 

 contain granules of the coloring matter 



THE BLOOD. 



... .A few drops are enough for microscopical examina- 

 tion. Prick the compressed linger, the ear of a rabbit or 

 the pads of a dog's foot ; take frog's blood directly from 

 the heart, otherwise it will contain a considerable 

 amount of lymph. 



To examiiie living blood. — . . . .Place a drop on a slide, 

 cover, and add a ring of paraffin to prevent evaporation. 

 Do this with blood of mammals and of frogs to show the 

 different shape of the red corpuscles. In a few minutes 



