498 History of Luminescence 



oxygen," but his gases were evidently impure. However, a sea- 

 water extract of the luminous parts in a long tube lost its lumines- 

 cence quickly, but the light would return on agitation, just as is 

 true for phosphorescence of the sea. In this case the bacteria had 

 used up dissolved oxygen in the tube and the light on agitation was 

 the result of additional solution of oxygen, when the surface of the 

 water was disturbed. 



Matteucci finally concluded that the fish luminescence was not 

 due to phosphorus but " to a substance which develops on putrefac- 

 tion, requiring for development the presence of oxygen, but which 

 shines without oxygen, by an action all but physical." It was dif- 

 ferent from phosphorescence of the sea which becomes more bril- 

 liant on adding ammonia, alcohol, etc., while the fish luminescence 

 disappears in their presence. Fish luminescence also persists at —2 to 

 —3° C, while sea luminescence stops at + 2 to + 3° C. Thus, Mat- 

 teucci discarded the possibility that the light might have come from 

 microorganisms. 



Fermentation and Putrefaction by Microorganisms 



Realization of the important part microorganisms play in con- 

 nection with changes after death was a very slow development. 

 Although Hooke described the mycelium of bread mold in Micro- 

 graphia (1665) , and Leeuwenhoek wrote to the Royal Society on 

 protozoa (1676), yeast cells (1680), and bacteria (1683), over 150 

 years elapsed before their activity in such common phenomena as 

 fermentation and putrefaction was appreciated. 



Yeast " globules " were again observed by Desmazieres in 1826, 

 but it is almost unbelievable that the recognition of yeast as a living 

 plant which reproduced by budding and was responsible for the 

 conversion of sugar to alcohol and carbon dioxide was not recog- 

 nized until the researches of Baron Charles Cagniard-Latour (1777- 

 1855) in 1836-1838. His findings were confirmed independently by 

 F. T. Schwann (1810-1882) and by F. T. Kiitzing (1807-1893) , both 

 in 1837. 



These discoveries were attacked by the chemists, J. J. Berzelius 

 (1779-1848) and J. Liebig (1803-1873), two of the greatest names 

 of the times. Berzelius in 1839 held that fermentation was an exam- 

 ple of the " catalytic principle " which he had announced in 1836, 

 and Liebig in 1839 published his own theory, which regarded " fer- 

 ments " as unstable molecules in a peculiar sort of vibration which 

 they communicated to other molecules, thus causing decomposition. 



Pasteur's monumental studies, beginning in 1857 and culminating 



