A manual of physiology : being a course of lectures / delivered by Prof. Küss ... ; edited by Mathias Duval ; trans. from the 2nd rev. ed. by Robert Amory.
- Küss, Emile.
- Date:
- 1875
Licence: Public Domain Mark
Credit: A manual of physiology : being a course of lectures / delivered by Prof. Küss ... ; edited by Mathias Duval ; trans. from the 2nd rev. ed. by Robert Amory. Source: Wellcome Collection.
Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.
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![Btead of producing electricity, there is, on the contrary, negative oscillation (as has been before remarked), that is a weakness or disappearance of the normal current of repose. In a nerve displaying activity, there appears to be a sort of molecular vibration which is propagated from point to point at the rate of 28 to 30 metres to the second. This molecular vibration extends both ways along the nerve] when the stimulus is applied midway, its existence is evi- dent only at the nervous extremity, where an organ suitable for its reception may be found ; as, for instance, towards the central end for sensitive nerves, and to the surface or periph- ery for the motor nerves. Thus it may be noticed that the terms centripetal and centrifugal depend upon the dif- ferent connections, and that both can conduct, indifferently, either way (Vulpian). 4. Excitants of the Nervous System. — Those excitants which can set in motion the functions of the nerves are numerous. Some of these are chemical, such as acids, ammonia, &c.; these agents, it will be seen, excite likewise the muscles, but in this case they need not be so concen- trated as in the former. Others may be in the nature of mechanical or physical excitants; as, for instance, a blow, electricity or heat. Electricity seems to excite the nerves only by the sudden changes it produces in their molecular condition; thus a current applied to a nerve affects its ac- tion, only when it begins or terminates its passage through the nerve; during its passage no action is evident. In order to excite nerves, sudden electrical discharges must be applied, and this is the reason for the employment of an induced current, frequently interrupted. At each interrup- tion, there ensues an excitation of the nerve. In normal physiological conditions, the external excitors are brought to bear upon the ends of the so-called sensitive nerves ; certain of the peripheral organs of this class (organs of special sense) exist where particular agents (light, sound, heat, odors, &c), give rise to special excitations. Finally, the central organs act as physiological excitants in the reflex order, where they only transmit previously received excitations, and in the phenomena called voluntary (which are doubtless a more or less complex form of reflex actions). This is due t;o the power which the nerve globules possess of storing up certain excitations (memory), whose manifesta- tions they allow only at a given time. We may perhaps](https://iiif.wellcomecollection.org/image/b21520938_0050.jp2/full/800%2C/0/default.jpg)
