Page:Proceedings of the Royal Society of London Vol 60.djvu/410

Rh material, like clouds of water on the earth, but in view of the high solar temperature it seems improbable that any body, except, perhaps, carbon, could exist in any condition other than the gaseous state in the solar atmosphere; so that it seems more probable that sun-spots are due, at least partly, to reflection by convection streams of gas, rather than by clouds of transparent solid or liquid particles.

The effects of a rise of temperature upon electrotonic currents may be briefly stated as follows:—

1. The ordinary electrotonic currents, A and K, are temporarily diminished or abolished at about 40°.

2. At about 30° of a rising temperature the K current is increased without notable alteration or with actual diminution of the A current.

3. On returning from 40° towards the normal (15° + 2°) temperature, the A and K currents reappear. K is increased and A is diminished, so that the previous normal inequality A > K is diminished, or actually reversed to A < K. In all cases the quotient A/K is diminished ; in some cases it actually falls below unity.

[The negative variation is temporarily abolished at about 40° ; a positive gives place to a negative variation in consequence of a raised temperature to 40°.]

The above three statements are illustrated by Experiments 2366, 2322, and, from the examination of their records, it will be clear that there is here no question of the effects being due to alterations of resistance. A and K are tested for alternately, and the deflection by O'OOl volt is taken at intervals of about ten minutes. [Other •examples of a similar character are given in the ‘ Proceedings of the Physiological Society’ for November, 1896, and a record of temporary diminution of the negative variation is given in fig. 12 {Experiment 777), ‘ Phil. Trans.,’ 1897.]

•ohms). The nerve lies upon four unpolarisable electrodes fixed at intervals of 12 mm., serving as leading-in electrodes to the polarising current and leading-out electrodes to the electrotonic current. On the galvanometer records, the anelectrotonic deflection A reads upwards, the katelectrotonic deflection K reads downwards; after-anelectrotonic and after-katelectrotonic deflections A' and K' read respectively downwards and upwards (there being under the conditions of experiment no marked homodromous after-katelectrotonic deflection).
 * In all the experiments referred to in this communication, the polarising current is by one Leclanclie cell (the resistance in its circuit being about 100,000