Densities of " Atmospheric Nitrogen" &c. 181 



the quick movement which may be regarded as an irregularly recurring 

 reflex that doubtless has among its objects the renewal of moisture on 

 the corneal surface, which otherwise would become dry. This natural 

 blinking movement seems in the monkey not to employ the orbital 

 portion of the orbicnlaris palpebramm, but only the palpebral. It occurs 

 habitually as a bilateral and symmetrical movement. It is far less 

 extensive in action than the closure of the palpebral opening, which 

 ensues when the monkey grimaces on being threatened with a blow. 

 That in the blinking the contraction of the palpebral part of the orbi- 

 cularis is not however the whole of the muscular mechanism 

 .at play, is clear from the fact, that in the awake and active animal 

 with fully opened eyes, the blinking still remains bilateral, subse- 

 quent to section of the facialis nerves of one side. The blinking by 

 the right eye was of course normal in character. As the right eye 

 blinked, the upper lid of the left eye quickly dropped three to four 

 millimetres over the globus of that side, and was then synchronously 

 with the lifting of the right upper lid lifted again. The left lower lid 

 was not on any occasion detected to move at all. The quick fall of the 

 upper lid of the left eye must have been due under these circumstances 

 to inhibition of the tonus of the left levator palpebrse superioris 

 muscle. This brings the co-ordination of the reaction into line with 

 that which I have described for other movements under the term 

 reciprocal innervation. 



It is interesting that Panas, Sappey, Fuchs, Wilmart and others, 

 who have carefully and particularly studied the mechanism of the 

 closure of the eye, have not attributed any share to an inhibition of 

 the levator palpebrse ; one physician, however, Dr. Lor, of Brussels, 

 lias argued that in the closure of the human eye such an inhibition 

 does under certain circumstances occur. 



" Note on the Densities of ' Atmospheric Nitrogen; Pure Nitrogen, 

 and Argon." By WILLIAM KAMSAY, F.B.S. Eeceive'd De- 

 cember 3, Eead December 15, 1898. 



M. A. Leduc in a recent paper* has discussed the relation between 

 .the density of argon, its proportion in atmospheric nitrogen, the den- 

 sity of the latter, and that of pure nitrogen. It appears to me that he 

 has misunderstood some of the data given by Lord Rayleigh, Dr. 

 Kellas, and myself ; and as the question whether the found density of 

 .argon corresponds with that calculable from the other data, is in itself 

 an interesting one, I have the honour to present this note to the 

 Society. 



* "Keeherclies sur les G-az," 'Ann. Chim. Phys.,' September, 1898. 



P 2 



