484 
PROFESSOR MATTEUCCl’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
the passage of the current. The apparatus which I have employed is that which 
Mons. Arago presented to the Acad6mie Royale des Sciences, in the sitting of the 
17th of September 1844, and the construction of which is due to the talent of Mons. 
Breguet. The apparatus principally consists of a solid brass support AB (fig. 1.) 
Fig. 1. 
Fig. 2. 
Fig. 3. 
fixed upon a wooden stand, in which slide two pieces of metal C, D capable of being 
fixed in different places by means of screws of pressure (vis de pression). The piece 
of metal C is furnished with a vice E, in which is to be held the morsel of spinal 
marrow of the prepared frog, and is fastened there by three screws. The other piece 
F, of a forked shape, is provided with a hole in each extremity of the fork, in which 
a very fine wire G is fixed or regulated. At one end of the wire is a hook to which 
is affixed the claw of the frog, the other end of the wire is attached to a silken thread 
which winds round the little pulley I. Upon this pulley another thread of silk is 
wound, in contrary sense to the former, and to this is attached a small leaden 
weight O. The axis of the pulley is furnished with a kind of double index PQ, in 
the form of a semicircle. The axis is fixed upon two pivols, which admit of being 
