579 



this matter, I shall content myself now with mentioning one result of 

 my inquiry, which I consider as well established ; the result, in fact, 

 of performing on muscles the same kind of experiment as the one 

 above described on the organ of the Torpedo. The experiment is as 

 follows : Having selected a series of muscles, entire or divided, 

 which have been proved (by my method of opposed muscular piles) 

 to be equal in electromotive power ; subject a certain number of them 

 to repeated stimulation, and then, by means of the method of opposed 

 couples, compare the muscles which have been exercised with those 

 which have been left at rest, and it will be found that the latter 

 will manifest a much greater degree of electromotive power than 

 the former. The nervous excitation, which causes muscular con- 

 traction, developes heat, generates mechanical force and consumes 

 . chemical affinity; and as the electromotive apparatus of muscle 

 operates through means of that affinity, it must get weakened, like a 

 pile in which the acid has become weaker. In the Torpedo, on the 

 other hand, there is neither heat nor mechanical force produced, and 

 the electromotive apparatus is set up again, as it were, through the 

 influence of the nerves, after the manner of a secondary pile." 



V. " Natural History of the Purple of the Ancients." By 

 M. LACAZE DUTHIERS, Professor of Zoology in the Faculty 

 of Sciences of Lille. Communicated by Professor HUXLEY. 

 Received March 22, 1860*. 



The purple dye so esteemed by the ancients has by turns excited 

 the curiosity of naturalists and of historians. The number of 

 memoirs upon the subject is considerable, and they are to be found 

 in almost all tongues. However, in all these works, remarkable in 

 many respects, and which cannot be analysed in this short notice, 

 three deficiencies are to be noted regarding matters of very great 

 moment in the history of this substance. 



What are, 1st, the producing organs? 2ndly, the nature? 3rdly, 



the natural primitive colour of the dye ? It is difficult to give any 



answer to these three questions by means of the facts contained in 



existing memoirs. It is for the purpose of replying to them that I 



* Translation received August 22, 1860. 



