ON INCREMENT OF ANIxMAL HEAT. 
413 
brought our instruments for observation to great perfection, 
and we have so attentively determined the temperature of 
the body in many diseases, that we know tlie thermal range 
of such diseases well. 
With all this we have much to learn : we have yet to arrive, 
in relation to animal heat, at what I may venture to call the 
engineering part of the question. We not only want to learn 
the bare fact that in such and such a malady there will be 
manifested such and such a temperature, but we want to be 
profoundly acquainted with the meaning of the whole subject. 
We want to know whether the rise of temperature or the fall 
of temperature, from the normal standard, is a cause of the 
other attendant phenomena, a coincidence or a sequence. We 
want to learn, above all things, again, what variations from the 
natural thermal standard, above it and below" it, the animal 
body will sustain ; what symptoms will run with each varia¬ 
tion ; what extremes of temperature wdll impede or stop the 
animal mechanism. I hope to elucidate these questions some¬ 
what, and I propose to-day to consider one of them so carefully 
as to leave on the mind a definite major fact and some minor 
facts. I propose to inquire what increment of animal heat 
w ill positively prevent motion in an animal, and w"hen we have 
found out satisfactorily I wmuld next try to discover the reason 
why a certain increment of heat did, as w e shall see it wdll, 
prevent motion. Before proceeding further, however, let 
me, having directed the eye to the point towards w"hich 
we are bending our way, make one or two preliminary 
explanations. 
1. Let me first explain that, in speaking of the increment 
of animal heat, I am not speaking of the degree of heat 
outside or surrounding man or other animal, in which 
life can or cannot be sustained, but that I am treating 
of the increment of heat which the animal body itself can 
bear. I shall, it is true, produce in some instances an incre¬ 
ment of animal heat, of heat within the animal body, by the 
addition of heat from without, but this only as a ready 
means for learning a fact; for I shall also show, in another 
lecture, that increment of heat in the organism may be 
induced in an ordinary temperature or medium by various 
changes in the body itself, as it is in every day disease. I press 
this explanation earnestly, because w'ithout it w"e shall not 
understand each other: think, then, nothing of the external 
temperature ; think only of actual animal temperature ; think 
of thermometrical readings only as they are derived from the 
animal body itself—from the mouth, the throat, or other 
part. 
