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much, to the chemical aspect of the phenomenon. Thus, Dar- 
win referred it to slow combustion of phosphorus, and found 
a confirmation in the existence of phosphoric acid in animal 
secretions. Recently, M. Schnetzler {Archives des Sciences 
Physiques de Geneve , 1855) attributed the light to combustion 
of phosphorus, on the ground that phosphates may be obtained 
from the destructive analysis of organic matter. This writer 
thought also that he had found phosphorus in the greasy sub- 
stance of the light- organs, which was more probably urate of 
ammonia in a state of phosphorescence. As regards the 
existence of phosphates, it is well known that all albuminous 
matter and many organic fluids contain phosphoric acid in 
combination with bases. 
Spallanzani regarded the luminous matter as a compound of 
hydrogen and carburetted gases. Thornton Herapath also 
believed the light to be due to a compound of hydrogen and 
carbon secreted by a particular gland organized for the purpose, 
and asserts that the most delicate analysis failed to show the 
slightest quantities of phosphates. The presence of phosphates, 
however (in cases where they are found), is unimportant, 
excepting their amount should much exceed that which tissues 
of a normal composition might be expected to yield to analysis, 
whilst the assumption of glandular apparatus for the secretion 
of carbo-hydrogens is entirely gratuitous, and contradicted by 
anatomical facts. The chemical evidence of the presence of a 
carburet of hydrogen is founded with more reason on the 
analysis of the fatty substance , but it has been already shown 
that light is not produced in the fatty bodies. The dis- 
tinction between common interstitial fatty matter and the 
albuminous parenchyma of the true light-organs has not been 
sufficiently recognized, and ignorance or disregard of this fact 
has occasioned a confusion of experiment, the different kinds 
of matter not being separately and comparatively examined. 
The difficulty of procuring sufficient for chemical analysis also 
interferes with the settlement of the question. Kolliker, how- 
ever, experimenting on the excised organs of as many as twenty 
to thirty insects at a time, positively denies the presence of 
any phosphorus, whilst the tests for albumen answered always 
affirmatively. Macaire long ago asserted the albuminous 
character of the light-organ, and, amongst other experimental 
results, notices that all agents which coagulate albumen annihi- 
lated the light-producing power. 
The continued production of light under conditions which 
render “ combustion,” as ordinarily understood, next to im- 
possible — as, for instance, in atmospheres of hydrogen and 
carbonic acid (Matteucci and Sir H. Davy), as well as the 
absence .of increased illuminating effect in an atmosphere of 
