238 ANNUAL OF SCIENTIFIC ^DISCOVERY. 



of the brown portion representing the clay growth of the hair, and 

 the white portion the night growth, and this opinion was corrobo- 

 rated by the remarks of Dr. Sharpey and others of the Fellows 

 who took part in the discussion which followed the reading. Un- 

 der the microscope the colors of the hair were reversed, the 

 brown became light and transparent, the white opaque and dark ; 

 and it was further obvious that the opacity of the white portion 

 was due to a vast accumulation of air-globules packed closely to- 

 gether in the fibrous structure of the hair, as well as in the me- 

 dulla. There was no absence of pigment, but the accumulation of 

 air-globules veiled and obscured the normal color and structure. 

 Mr. Wilson observed that, as the alteration in structure, which 

 gave rise to the altered color, evidently arose in a very short pe- 

 riod, probably less than a day, the occurrence of a similar change 

 throughout the entire length of the shaft would explain those re- 

 markable instances, of which so many are on record, of sudden 

 blanching of the hair ; and he ventured to suggest that during the 

 prevalence of a violent nervous shock the normal fluids of the 

 hair might be drawn inward toward the body, in unison with the 

 generally contracted and collapsed state of the surface, and that 

 the vacuities left by this process of exhaustion might be suddenly 

 filled with atmospheric air. Dr. Sharpey mentioned a recent ex- 

 ample of sudden blanching of the hair, which had been observed 

 by Dr. Landois, of Greifswalde, as reported in Virchow's Archiv, 

 and which was ascertained to be due to accumulation of air- 

 globules in the fibrous substance of the hair. Lancet. 



MIND AND CORRELATION OF FORCE. 



In a lecture delivered at the Royal Institution, on the "Doc- 

 trine of the Correlation of Force in its bearing on Mind," Prof. 

 Alexander Bain shows that the extension of that correlation to 

 mind must be made through the nerve-force. According as the 

 mind is exerted, force is drawn away from the proper corporeal 

 functions, which arc to that extent weakened. We all know by 

 common experience that great mental exertion is rarely combined 

 with great physical robustness ; neither do we find many exam- 

 ples of a combination of different modes of mental excellence. 

 Leonardo da Vinci was a great artist and a great man of science ; 

 but how few have there been like him ! Great sensibility is sel- 

 dom associated with great activity of temperament, nor intellec- 

 tual originality with emotional exuberance. 



NEAR AND FAR-SIGHTEDNESS. 



Until recently "near-sightedness" and "long-sightedness" 

 have been explained by assuming in the first case that in conse- 

 quence of the too great convexity of the cornea and crystalline 

 lens, one or both, the focus is formed in front of the retina, while 

 in the second the rays of light are concentrated behind the retina, 

 because the convexity of the parts just mentioned is too small. 

 The correction of these imperfections by the use of concave 

 glasses in the first instance, and of convex ones in the second, 



