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CHAPTER I. 
EMISSION OF LIGHT BY DEAD ANIMAL MATTER. 
Ty this section of my work I shall speak of the 
emission of ight by dead animal matter, before 
entering upon the subject of phosphoric animals. 
It is well known that when the dead bodies of 
certain fish, more especially mackerels and her- 
rings, are exposed to the air for a short time, 
they soon become luminous in the dark. When 
they are in this state, if we merely rub the finger 
over the luminous surface of the dead fish, we re- 
cognize the presence of an oily substance, which 
renders the finger luminous, as if it had been 
rubbed upon phosphorus. 
This grease, when separated from the body of. 
the fish by means of a knife, and placed upon a 
plate of glass, continues to shine in the dark. 
When examined under the microscope, not a ves- 
tage of infusoria or other animalcule is seen in it, 
which otherwise, as we shall see further, might 
account for its luminosity. 
