THE GLOWWORM'S LIGHT- EM LTTING APPARATUS. 323 
oxygen (Beckenheim, Dr. Hulme, and Sir H. Davy) — are facts 
directly opposed to this hypothesis. On the other hand, all 
experiments tending to demonstrate the direct influence of 
nerve stimulation by external physical agents, as well as those 
which prove the paralyzing effect of narcotics on the nerves, 
go far to establish the theory of nerve function, or at least 
of nerve regulation of the metamorphosis of tissue which 
supports the function. 
If the “ slow combustion ” (Matteucci and Roberts) be inter- 
preted as oxidation of animal matter undergoing metamor- 
phosis, the whole series of experiments apply without contra- 
diction. The activity of function is checked by everything 
which interferes with oxidation, lessens nerve sensibility, or 
destroys the normal condition of tissue. Thus, when the 
light-organ is kept in vacuo, under water or oil, the illumi- 
nating effect gradually diminishes, as also when the substance 
is painted with a solution of gum, or the substance allowed to 
dry up. The latter state (pointed out by Caradori, Kolliker, 
and many others) has been particularly dwelt on by Carus in 
his communications to the Academy of Sciences in Paris. That 
the luminous matter loses its phosphorescent property when 
dried, but regains it when moistened in water, may perhaps be 
explained by the temporary disturbance of the naturally semi- 
fluid albuminous matter, and its consequent loss of capacity to 
undergo oxidation and metamorphosis without being actually 
destroyed. Carus notices that the experiment can only be 
performed once with the same matter, a circumstance which 
shows that the limit of action is connected with organic con- 
ditions rather than with chemical constitution of the luminous 
substance. For if the substance were independent of organic 
influence, the production of light might be expected to continue 
so long as phosphorescent matter is present. 
So also in respect to the effect of heat or cold on the pro- 
duction or extinction of light. As the frozen insect revives by 
the warmth of the hand (Kolliker), the power of emitting light 
reappears. The effect of heat or cold is chiefly marked when 
change of temperature has been rapid and great within a given 
time, and belongs, therefore, to the known laws of action of 
temperature on living bodies. Heat and cold are relative stimu- 
lants or depressors of vital action. 
Macartney, rejecting the theory of combustion, either chemical 
(as of phosphorus or carburetted hydrogen) or organic, sug- 
gests that the light is rather a quality of matter than a 
substance. 
Brugnatelli (1797) believed that the phosphorescence of the 
Lampyridse was due to a peculiar physiological act, by which 
these insects separated light from their food. In modern 
