Royal Society. 293 



plained somewhat fully and illustrated by experiments on para- 

 magnetics of sufficient inductive capacity to manifest the effects 

 of mutual influence, at the meeting at Belfast) as an abstract of 

 my communication, for publication in the Report of the Belfast 

 meeting of the British Association, where you may see them 

 stated, I hope intelligibly. The experiments on the paramag- 

 netics are very easy, and certainly exhibit some very curious 

 phamomena, illustrative of the resultant effects due to the attrac- 

 tions experienced by the parts in virtue of a variation of the 

 intensity of the field, and to the couples they experience when 

 their axes are diverted from parallelism to the lines of force by 

 mutual influence of the magnetized parts. 



I had no intention of entering on this long disquisition when 

 I commenced, but merely wished to try and briefly point out, 

 that the assertions I have made regarding mutual influence are 

 demonstrable in every case without special experiment, are con- 

 firmed amply by experiment for paramagnetics, and are abso- 

 lutely incontrovertible, as well as incapable of verification, by 

 experiment or observation on diamagnetics. 



Believe me, yours very truly, 



William Thomson. 



Prof. Tyndall. 



* 



XLV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 236.] 



Dec. 14, 1854. — The Lord Wrottesley, President, in the Chair. 



f T , HE following communication was read : — "The Physical Theory 

 ■* of Muscular Contraction." By Charles Bland RadclhTe, M.D. 



The theory set forth in this paper is, that muscle is prevented from 

 contracting by the several vital and physical agencies which act as 

 stimuli upon muscle, — volition, nervous influence, blood, electricity, 

 light, heat, and the rest, — and that contraction happens on the cessa- 

 tion of stimulation, by virtue of the operation of that universal prin- 

 ciple of attraction which belongs to muscle in common with all 

 matter, and, so happening, that it is a physical phenomenon of the 

 same nature as that contraction which takes place in a bar of metal 

 on the abstraction of heat. 



This theory is supported by various arguments, some of which 

 are now stated for the first time. It is argued : — 



(a.) That nervous influence cannot cause muscular contraction, 

 (1) because the degree of innervation, as measured by the supply of 

 nerves, is inversely related to the tendency to contraction ; (2) be- 

 cause contraction does not take place so long as the nerve gives 

 evidences of electricity (J)u Bois Reymond); (3) because, in some 

 instances at least, contraction does not happen so long as the nerve 



