EEE ROG, 
The following directions refer more particularly to Rana 
pipiens, but can be used with other species of frog if desired. 
In the following pages, the terms right and left refer to the 
right and left sides of the frog, not of the observer. The term 
dorsal means the side that is ordinarily uppermost during life; 
ventral means the side that is ordinarily kept toward the earth. 
The anterior end of the body is the one pointing in the direction 
in which the animal ordinarily moves (1. e., the head end, termi- 
nating in the snout), as opposed to the posterior end. Medial is 
used to indicate nearness to the middle line; lateral is the con- 
trasting term. Proximal refers to that part of an organ or 
structure nearest to its center or to its attachment to the body; 
distal is the opposite adjective. 
I. ATTITUDES AND MOVEMENTS. 
Notice the normal resting position of the living frog, especially 
the attitudes of the fore and hind limbs. ‘Induce a frog to leap; 
how is this movement effected? Are any preparatory movements 
required? What is the significance of the normal resting 
position? 
Describe the attitude of a frog resting at the surface of deep 
water. How much of the frog is above water? What is the 
advantage of the protrusion or bulging of the eyes? Can the 
frog in this position secure air? When a frog in this position is 
alarmed, it will dive quickly to the bottom. Describe in detail the 
successive movements by which this is accomplished. What is 
the significance of the resting position at the surface of deep 
water? 
Study the respiratory movements and explain fully how air is 
taken into and expelled from (a) the mouth, and (b) the lungs. 
The frog does not possess ribs and is unable to enlarge the cavity 
of the body directly ; hence it employs an indirect method of filling 
the lungs, which can be made out by a careful study of the move- 
S) 
