BLOOD AND LYMPH. 9! 



Amoeboid Movements. These are most conveniently 

 studied in the blood or lymph from one of the cold- 

 blooded animals, such as the frog, for they occur here at 

 the ordinary temperatures of the air, while artificial heat 

 must be resorted to if we would maintain the blood of 

 warm-blooded animals and a proper temperature for their 

 occurrence. 



The leg and toes of a frog having been carefully 

 cleansed, the tip of one of the toes is snipped off, and on 

 stripping the leg downward with the thumb and finger, 

 a drop of mixed blood and lymph will presently exude 

 from the toe. This is received on a slide, protected from 

 pressure by a bit of hair, and covered. To prevent 

 evaporation of the plasma, a rim of oil is painted around 

 the edge of the cover. On focussing now upon the 

 specimen, white blood-cells will readily be found, and 

 selecting one which, by its irregular shape, indicates its 

 activity, the attention must be fixed upon this cell and 

 sketches of its form made at short intervals every two 

 minutes. Although the movement is usually too slow to 

 be actually detected by the eye, if the cell is fairly active, 

 it will be sufficiently evident, after a few sketches, that it 

 has changed its shape and perhaps its place also. 



If the temperature of the room be low, the movements 

 may be tardy in commencing, and they can be hastened 

 by holding the finger or any warm object for a moment 

 near the cover. It should be borne in mind that in the 

 frog's blood the red cells are oval and nucleated, and that 

 they are also larger than the colorless cells. 



Fibrin. A small quantity of blood may be whipped 

 and the cells washed from the clot by a stream of water, 



