M. C0. Lea—Aetion of Light upon Silver Bromide. 483 
until delirium ends in persistent unconsciousness, simultane- 
ously with cold perspiration and relaxation of the sphincters. 
5. The mode of death is by asthenia in both forms of rabies; 
but in R. canina the frightful struggles of nature to eliminate 
the poison are more prolonged than in R. mephitica ; and in the 
latter they may, on occasion, be still further abridged by the 
use of morphine, which has no narcotic effect upon the former, 
even in the largest doses and injected into the veins! 
ave thus endeavored to describe, and also to explain, 
these strange and painful phenomena. I must leave the reader 
to form his own decision, only hoping that some one may 
induced to follow this pioneer work in a new path, by further 
and more able investigations of his own. 
Kansas City, Mo., Feb. 24th, 1874. 
Art. XLV.—On the nature of the action of Light upon Silver 
Bromide; by M. Carey LEA, Philadelphia. 
WuEN silver bromide is exposed for a moment to light, it 
undergoes no visible change, but has acquired the property of 
passing to an intense black when treated with pyrogallic acid 
and an alkali. : 
the nature of this black substance, there has existed 
considerable diversity of opinion. In a paper published on the 
subject about a year since by Captain Abney, F.C.S., he ex- 
mide, not an oxide, probably the former. _ 
The existence of these compounds is evidently an argument 
for doubling the atomic weight of silver, as has recently been 
on other grounds. 
Am. Jour. Sor—Turap Sante Vou. VII, No. 41.—Mar, 1874. 
