603 



movement remained the same. I then divided the two nerves as 

 high as possible, and, afraid that there might be some small blood- 

 vessels still giving blood to the nerves, I dissected the whole length 

 of their trunk for the second time. Near the section, the nerves 

 remained able to cause muscular contractions for seven hours. 



Experiments more or less similar to this one have given very 

 nearly the same results, and I am therefore led to conclude that, with 

 the least quantity of blood, motor nerves retain their vital property 

 very much longer than muscles. If motor nerves in a limb 

 separated from the body of a living animal seem to lose their vital 

 property sooner than muscles, it is because, as I will prove in 

 another paper, the transmission of the nervous force from the last 

 nervous ramifications to the contractile elements of muscles, soon 

 becomes impossible in the absence of blood charged with oxygen. 



From the facts above related, and from many others, I think I am 

 entitled to conclude that the vital properties of motor and sensitive 

 nerves may last longer without blood than muscular irritability. 



VII. " Ocular Spectres, Structures and Functions, Mutual 

 Exponents." By JAMES JAGO, A.B. Cantab., M.B. Oxon., 

 Physician to the Royal Cornwall Infirmary. Communicated 

 by R. WERE Fox, Esq., F.R.S. Received August 22, 

 1857. 



(Abstract.) 



SECTION I. Introduction. 



Our visual organs are not only capable, by an adjusting 

 lenticular system, of painting, under varying conditions, images of 

 luminous objects, upon a membrane in special relation with the 

 brain, but involve many adjuvant structures ; and thus it happens 

 that they reveal to us a number of adventitious phenomena 

 spectres as we may call them, whether caused by light at the 

 parts that cover the eyeballs, or within them, or by anv stimulus 

 whatever affecting the special nervous tract. These must be elimi- 

 nated, if we woidd avoid the risk of ascribing effects begotten 

 by subordinate parts to more integral portions of the apparatus. 



VOL. viii. 2 x 



