
CHAPTER VIE 
4HE LIMITS OF VITAL RESISTANCE TO HEAT: EARLY 
OBSERVATIONS 
fl Gece all-important question of the destructive 
influence of heat upon living matter requires 
to be looked at from a broad point of view, because 
of the essential unity of protoplasm. As Huxley 
said, ‘Beast and fowl, reptile and fish, mollusc, 
worm, and polype, are all composed of structural 
units of the same character, namely, masses of 
protoplasm with a nucleus. . . . What has been said 
of the animal world is no less true of plants... . 
Protoplasm simple or nucleated is the formal basis 
of all life. . . . Thus it becomes clear that all living 
powers are cognate, and all living forms are funda- 
mentally of one character.” If, therefore, we can 
show that the limits of vital resistance to heat for 
very many different representatives of the animal 
and the vegetal kingdoms fall within comparatively 
narrow limits, we shall be doing our best to establish 
a sound induction concerning the thermal death- 
point of living matter generally—and thus to 
discredit the vague or extravagant statements that 
are apt to be made on this subject. 
In the latter third of the eighteenth century a 
1 “ Lay Sermons,” pp. 126-129. 
43 
