80. REPORT—1852, 
bear to each other a similar relation as the production of magnetism in a bar of per- 
fectly soft iron and that in a bar of steel, by means of an electric current passed 
through a coil surrounding the bar. Suppose, indeed, that a current be passed 
through a coil surrounding a very short portion of a long bar of soft iron, the bar 
will directly prove magnetic in its whole length, only the intensity of its magnetic 
force will decrease from the coil to the two ends of the bar. As soon as the circuit 
of the coil has been broken, the bar would be found quite bare of any magnetic power, 
provided the iron be perfectly soft; in making the experiment, however, there will 
still be some magnetism left. Again, suppose that the same coil were placed in the 
same manner on a similar bar of steel, instead of soft iron, then its action would 
not extend over the whole length of the bar, only the very portion surrounded by 
the coil, and those placed in its immediate neighbourhood, would become magnetic ; 
but in this case they would remain so even after the circuit of the coil had been 
broken. 
This difference in the magnetic phenomena elicited in steel and iron by the electric 
current, philosophers are in the habit of ascribing to a coercitive force possessed by 
the former substance, by which force the magnetic fluids are prevented from moying 
freely so as to require a certain amount of force to be separated, and to remain so 
afterwards ; or by which force, to speak in accordance with Ampére’s theory, the 
molecules surrounded by currents, on which the magnetic phenomena are admitted 
to depend, are kept in the positions in which they once have been put by any pre- 
vious action. It therefore may be concluded, that with respect to the mobility of 
their electromotive molecules, the muscles and nerves differ from each other in the 
same way as steel and soft iron; or that the muscles possess a coercitive force which 
prevents their electromotive molecules from moving as freely as they seem to do in 
the nerves. 
This statement appears the more important, as I had hitherto not succeeded in 
pointing out any essential difference between the electrical phenomena of muscles 
and nerves. Yet such a difference ought to exist, if any relation be admissible be- 
tweer the electrical phenomena of muscles and nerves, and their other vital properties, 
which present such striking discrepancies. 
On the Forces by which the Circulation of the Blood is carried on. 
By Professor T. Wuarton Jonzs, F.R.S. 
On the State of the Mind during Sveep. 
By Ricuarp Fow er, .D., F.R.S. 
What is the state of the vital and mental forces during sleep, dreaming, trance, 
asphyxia, coma, compression of the brain, intoxication ? 
The body of an animal is its coil (“ mortal coil”’), and this, like a federative re- 
public, of which the brain coil is the chief, is composed of a congeries of coils (organs 
of sense, glands, &c.), and, above all, of a muscular apparatus so adjustible as to 
enable the mental force to form it into coils for occasional purposes, for expression 
by speech and gesture, execution of works of art, &c. 
In its waking state, the mental force has indirect perception of the adjustments 
of the muscles by the muscular sense, rendered more sensitive by the blood accom- 
panying every retransmission to the muscular and nervous fibres. 
The mental force has, in addition to perception and volition, a power to modify 
the adjustments induced by sensations and conceptions. It has its sense of buoyancy 
and fatigue from the different degrees of compression felt on the sentient extremi- 
ties of the muscular nerves, hence the idea of power. Hume challenged the as- 
sertors of our having an idea of power to adduce the impression from which it may 
be inferred ; and here is an adequate impression. 
That mind and vitality are forces, is ascertained by the resistance they can oppose 
to all the physical forces, to those of gravitation and motion, by mounting a hill or 
swimming against a rapid stream, by the heavier weight sustained by a living than 


