. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. THE NERVOUS SYSTEM—GENERAL CONSIDERATIONS. 213 the frog hang in the liquid; after a few moments it will be withdrawn. 4. Repeat, holding the leg; probably the other leg will be drawn up. 5. Apply stronger acid to the inside of the right thigh; the whole frog may be convulsed, or the left leg may be put in action after the right. Even if the stimulating paper be applied near the anus, it will be removed by the hind- legs. 6. Beneath the skin of the
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. THE NERVOUS SYSTEM—GENERAL CONSIDERATIONS. 213 the frog hang in the liquid; after a few moments it will be withdrawn. 4. Repeat, holding the leg; probably the other leg will be drawn up. 5. Apply stronger acid to the inside of the right thigh; the whole frog may be convulsed, or the left leg may be put in action after the right. Even if the stimulating paper be applied near the anus, it will be removed by the hind- legs. 6. Beneath the skin of the back (posterior lymph-sac) inject a few drops of liquor strychnise of the pharmacopoeia; after a few minutes apply the same sort of stimulus to the thigh as before. The effects follow more quickly and are SENSORY CENTRE" INHIBITORY CENTRE. SENSORY CELL AND AFFERENT NERVE MOTOR CELL AND EFFERENT NERVE MOTOR CELL WITH EFFERENT NERVE Fig. 195.—Diagram intended to illustrate nervoiis mechanism of—1, automatism; 2, reflex action ; and 3, how nervous impulses in the latter case ma^ i)ass into the higher parts of brain and become part of consciousness, or be wholly inhibited. A reflex or autoniatic center may for the sake of simplicity be reduced to a single cell, as above on the left. much more marked—the animal, it may be, passing into a gen- eral tetanic spasm. These experiments may be varied, but suffice to establish the following conclusions: 1. The stimulus is not immediate- ly effective, but requires to act for a certain variable period, depending chiefly on the condition of the central nervous sys- tem. 2. The movements of the muscles harmonize (are co-ordi- nated), and tend to accomplish some end—are purposive. If. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mills, Wesley, 1847-1915. New
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