ON THE EARLY STAGES OF INFLAMMATION 265 
been brought into the field where there were two considerable groups of cells 
in moderate activity, the cautery was again applied at a distance of about 
24 inches. The motions of the cilia immediately became distinctly increased, 
but, as in the former case, this condition gave place in five seconds to universal 
quiescence. The iron was then removed, and on re-examination after three 
minutes, the cilia were again moving, though in a somewhat languid manner 
in both parts of the field. For the sake of confirmation I again operated in 
a similar manner upon another specimen, on which I performed no less than 
five successive experiments with similar results in all. In the first three of 
these trials I had the very same cilia under observation, and saw them time 
after time become first increased in action and then arrested under the influence 
of the cautery, and gradually recover after its removal. In some instances the 
times of cessation and of recovery were noted as follows :—In the first the 
cilia were arrested in two seconds after the application of the hot iron, but 
the exact time of recovery was not observed ; in the second, cessation of move- 
ment was produced in two seconds, and return began in fifteen seconds ; in 
the third, cessation was in fifteen seconds, and recovery also in fifteen seconds ; 
in the fourth, the times were not noted ; in the fifth, movement ceased in about 
two seconds and returned in twenty. The experiments were performed within 
about five minutes of each other, or something less. It is also to be remarked, 
that there were some slight differences in the degree of heat of the cautery 
and its vicinity to the object. 
These experiments are as instructive as they are simple and easy of per- 
formance. They show conclusively that a component tissue of the animal 
frame may, independently of the nervous system, have its actions either excited 
or paralysed by the direct operation of an irritant upon it, and that it may 
possess an equally independent power of recovery. Also in the accelerated 
movements of the cilia elicited by very gentle heat, as compared with the cessa- 
tion of their vibrations under a higher temperature, we have a striking con- 
firmation of the view which I had taken of the relaxation of the arteries and 
hollow viscera in consequence of nervous irritation.! For the law which we 
thus see regulating the effects of heat upon the epithelium-cells is precisely that 
which I had inferred must govern the action of afferent nerves upon nerve- 
cells ; this law being, that an agency which, when operating mildly, stimulates 
a tissue to increased activity, may, when more energetic, temporarily arrest 
its functions. Whether or not the converse always holds, viz. that any agent 
which is capable of suspending the functional activity of a tissue may also 
excite it if applied with sufficient gentleness, or, in other words, whether irritants 
' Vide antea, p. 232. 
