PHYSICS OF THE BRAIN. 
419 
temporarily destroyed in parts or sections. Then I and another 
physiologist, Dr. Weir Mitchell, of Philadelphia, took up simul- 
taneously and independently the study of brain function by 
destruction of part. The truths thus learned, in so far as they 
relate to my own work, I would now record. I put them for- 
ward as being yet limited, but not valueless. 
I shall begin the narrative best by stating that the brain 
matter contains two substances which admit of solidification by 
cold, viz., water and fatty matter. These solidify at different 
temperatures, but both are entirely frozen by reducing the 
temperature to 16° Fabr. or 16° below freezing point. At this 
degree all the water of the nervous structure, amounting to 84 
per cent, of the whole, is crystallized as ice ; in this condi- 
tion the structure is for the time dead, it is as though it were 
removed from the body altogether. 
Suppose, then, that we bring into this state of temporary 
death the front part of the brain, the two lobes or hemispheres 
of the cerebrum or larger brain, which mainly fill the skull. 
The phenomena produced are those indicating entire loss of 
volition, of sensation, of all that may be considered intelligence. 
To appearance the animal profoundly sleeps, it is as if it were 
under the ( influence of chloroform or ether, and an operation of 
any kind may be performed upon it without pain. It may, 
nevertheless, move when handled, and it may show a kind of 
involuntary life due to what is called spinal action, to some power 
resident in the spinal cord. A frog thus circumstanced will 
sometimes leap ; but warm-blooded animals, as a general rule, 
will remain like as in catalepsy, always retaining the position 
in which they last were left. 
In cold-blooded animals, as in the frog, when the functions 
of the brain are entirely suspended, the freezing process may be 
carried to and through the spinal cord, and every portion of the 
nervous system may thus be deprived of force, the animal re- 
maining motionless, rigid, and indeed like stone. In this state 
it would remain, I believe, for an unlimited period of time if it 
were kept under the same condition of temperature ; but from 
this extreme condition of shrunk death it will, nevertheless, re- 
cover on gradual restoration of warmth. In some warm-blooded 
animals we see an approach to this same state, naturally brought 
about in the period when they are hybernating, in the profound 
sleep of the cold season ; but there is this difference, the 
animal, during hybernation, still breathes, and still takes in some 
air for respiration, without which it could not recover with the 
return of warmth. And we find by experiment that if the pro- 
cess of freezing artificially be carried on in a warm-blooded 
animal, from the brain into the spinal system, so as to stop 
VOL. VI. — NO. XXV. H H 
