Things not generally Known. 



of a second passes after the receipt of the command before the 

 muscle is in activity. In all, therefore, from the excitation 

 of the sensitive nerves till the moving of the muscle, 1^ to T %ths 

 of a second are consumed. Intelligence from the great toe ar- 

 rives about g^th of a second later than from the ear or the face. 

 Thus we see that the differences of time in the nervous im- 

 pressions, which we are accustomed to regard as simultaneous, 

 lie near our perception. We are taught by astronomy that, on 

 account of the time taken to propagate light, we now see what 

 has occurred in the fixed stars years ago ; and that, owing to 

 the time required for the transmission of sound, we hear after 

 we see is a matter of daily experience. Happily the distances 

 to be traversed by our sensuous perceptions before they reach 

 the brain are so short that we do not observe their influence, 

 and are therefore unprejudiced in our practical interest. With 

 an ordinary whale the case is perhaps more dubious ; for in all 

 probability the animal does not feel a wound near its tail until 

 a second after it has been inflicted, and requires another second 

 to send the command to the tail to defend itself. 



PHOTOGRAPHS ON THE EETINA. 



The late Rev. Dr. Scoresby explained with much minute- 

 ness and skill the varying phenomena which presented them- 

 selves to him after gazing intently for some time .on strongly- 

 illuminated objects, as the sun, the moon, a red or orange or 

 yellow wafer on a strongly-contrasted ground, or a dark object 

 seen in a bright field. The doctor explained, upon removing 

 the eyes from the object, the early appearance of the picture or 

 image which had been thus "photographed on the Retina/' 

 with the photochromatic changes which the picture underwent 

 while it still retained its general form and most strongly-marked 

 features ; also, how these pictures, when they had almost faded 

 away, could at pleasure, and for a considerable time, be renewed 

 by rapidly opening and shutting the eyes. 



DIRECT EXPLORATION OF THE INTERIOR OF THE EYE. 



Dr. S. Wood of Cincinnati states, that by means of a small 

 double convex lens of short focus held near the eye, that or- 

 gan looking through it at a candle twelve or fifteen feet distant, 

 there will be perceived a large luminous disc, covered with 

 dark and light spots and dark streaks, which, after a momen- 

 tary confusion, will settle down into an unchanging picture, 

 which picture is composed of the organs or internal parts of the 

 eye. The eye is thus enabled to view its own internal organis- 

 ation, to have a beautiful exhibition of the vessels of the cor- 

 nea, of the distribution of the lachrymas secretions in the act 



