on THE VASCULAR SYSTEM OF THE FROG. 
E. Microscopic Examination of Blood. 
I. Frog’s Blood. 
1. Normal. 
Place on a slide a small drop of blood from the heart of a frog: 
dilute it with a drop of normal salt solution (0°75 per cent.) : put 
on a thin coverglass and run a ring of ol round the edge to pre- 
vent evaporation. examine with high power, and note :-— 
The blood corpuscles floating in the colourless liquor 
sa guinis or plasma. The corpuscles are of two 
kinds. 
i. Red corpuscles; very numerous: pale reddish 
or yellowish red colour: flattened oval shape, 
with rounded edges and a central bulging—the 
nucleus. The flattened shape is best seen when 
a corpuscle turns edgeways. Size roo X 1700 
of an inch. 
ii. White corpuscles: much fewer in number and of 
smaller size: colourless : granular: subspherical 
in shape: exhibiting “ameeboid” movements. 
Sketch one half a dozen times at intervals of half 
a minute. 
2. Action of acetic acid on blood. 
Place a fresh drop of blood on a clean slide: add a drop of 
acetic acid : cover, and examine with high power : note the changes 
produced :— 
i. Red corpuscles: the nuclei become much more 
apparent than before: the red colour disappears. 
ii. White corpuscles: become clearer: show nuclei, — 
sometimes more than one in a single corpuscle. 
II. Human Blood. 
1. Normal, 
Prick the tip of your finger and place a small drop of the blood 
on a slide: add a drop of normal salt solution, cover, and 
examine as before. Note -— 
i. Red corpuscles: much smaller than in frog’s 
blood: in form of circular biconcave discs with 
