By Addison Earl Lee
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Extra info for Development and structure of the frog: a photographic study
Example text
The rat with a small brain is more intelligent than the whale with a large brain. The most impor tant size index correlated with intelligence is the ratio· of the brain weight to the spinal cord weight. In the frog, this is less than 1: 1, while in man it is 55: 1. Probably the most important comparison is the development of respective individual parts of the brain as illustrated on the following page. If the cere brum of the frog is removed, the animal behaves very much as a normal animal. But if the cerebrum of man fails to de velop properly, the individual is severely handicapped men tally.
E :E "' ... .... "' :z:: 37 FROG PERCENT MAN OF TOTAL BRAIN WEIGHT 31 V. Experiments with Frogs A MUSCLE AND NERVE ACTIVITY Numerous experiments can be performed to illustrate muscle activity and the relationship between nerves and muscles. In order to do these experiments, it is necessary to make a mus cle preparation as illustrated in photographs A through G on pages 33 and 34. The gastrocnemius muscle is commonly used. Remove the head (see page 39) , or pith the animal and cut through the skin around the upper hind leg.
The muscle should then be placed in Ringer's solution until ready for use. 5 g. 14 g. 12 g. CaCl2 in one liter of distilled water. To experiment with this preparation, place the gastrocnemius muscle (193) in an arrangement a,s illustrated in photograph G. The weight (194) is used to stretch the muscle to proper tension. It may be moved to the right or left to increase or de crease this tension. ) , and touch the muscle preparation with the electrodes (196) . Increase the stimulus from the inductorium until a greater response is no longer obtained with increased strength of the stimulus.