432 Prof. Huxley, on the 'present state of Knowledge [May 15, 



to prevent a grey design acquiring a pinkish shade through working 

 it with green, give the grey a greenish hue, which, by neutralising 

 the pink, will generate white light, and thus preserve the grey. 



Mr. Grace Calvert, after explaining the chromatic table of M. 

 Chevreul, which enabled any person at a glance to ascertain what, 

 was the complementary colour of any of the 13,480 colours which 

 M. Chevreul had distinctly classed in his table, stated that it was 

 of the highest importance to artists to be acquainted with these 

 laws, in order to know at once the exact colour, shade, and tint, 

 which would produce the greatest effect when placed beside another 

 colour, and that they could save the great length of time which no 

 doubt the great masters lost in ascertaining by experiment those 

 laws, which they could now learn in a few hours by consulting 

 M. Chevreurs work. 



[F. C. C] 



WEEKLY EVENING MEETING, 

 Friday, May 15. 



The Lord Wensleydale, Vice-President, in the Chair. 

 Thomas H. Huxley, F.R.S. 



FULLEBtAN PROFESSOR OP PHYSIOLOGY BOYAL INSTITUTION. 



On the present state of Knowledge as to the Structure and 

 Functions of Nerve, 



The speaker commenced by directing the attention of the audience 

 to an.index, connected with a little apparatus upon the table, and 

 vibrating backwards and forwards with great regularity. The 

 cause of this motion was the heart of a frog (deprived of sensa- 

 tion though not of life) which tiad been carefully exposed by open- 

 ing the pericardium, and into whose apex the point of a needle 

 connected with the index had been thrust. Under these circum- 

 stances the heart would go on beating, with perfect regularity and 

 full force, for hours ; and as every pulsation caused the index to 

 travel through a certain arc, the effect of any influences brought to 

 bear upon the heart could be made perfectly obvious to every one 

 present. 



The frog's heart is a great hollow mass of muscle, consisting of 

 three chambers, a ventricle and two auricles,the latter being separated 

 from one another by a partition or septum. By the successive con- 



