. Elements of human physiology. Physiology. 174 PHYSIOLOGY application of the current cause slight apparent irregularities in the law of contraction as tested on man. Other Methods of Stimulation 1, Thermal. If the temperature of a nerve be gradually raised, no effect is noticed till about 40' C. is reached, when the muscle may enter into weak quivering contractions. Sudden warming of the nerve always gives rise to excitation. At about 45° C. the nerve loses its irritability and dies. A nerve may be rapidly cooled without any excitation taking place. At about 0° C. the conductivity of mammalia
. Elements of human physiology. Physiology. 174 PHYSIOLOGY application of the current cause slight apparent irregularities in the law of contraction as tested on man. Other Methods of Stimulation 1, Thermal. If the temperature of a nerve be gradually raised, no effect is noticed till about 40' C. is reached, when the muscle may enter into weak quivering contractions. Sudden warming of the nerve always gives rise to excitation. At about 45° C. the nerve loses its irritability and dies. A nerve may be rapidly cooled without any excitation taking place. At about 0° C. the conductivity of mammalian Fig. Electrodes applied to the skin over a nerve-trunk. In a the polar area is anelectrotonic and the peripolar katelectrotonic. The former condition therefore preponderates, since the current here is more concentrated. In b the conditions are reversed, the polar zone corresponding in this case to the kathode. (Waller.) nerve-fibres is absolutely abolished, and hence this method of cooling is of great value when it is required to divide a nerve physiologically without exciting it. 2. Mechanical. A nerve may be excited by crushing or cutting. These methods however destroy the nerve. It is possible to excite a nerve mechanically, without any serious injury to it, by carefully graduated taps, and this method has been used in investigating the phenomena of electrotonus. 3. Chemical. All chemical stimuli applied to the nerve. 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 Starling, Ernest Henry, 1866-1927. Chicago : W. T. Keener
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