200 History of Luminescence 



Meeres mit hesonderer Hinsicht auf das Leuchten tierischer Korper, 

 a pamphlet of 182 pages published at Gottingen in 1803. The title 

 page is reproduced as figure 18. According to Heinrich (1815, p. 

 387) , this was presumably an answer to a prize question and was 

 quite superior to other papers of the time, but the author has been 

 unable to locate the donor of the prize. It is divided into six parts, 

 with Parts I to V devoted to sea light, leaving Part VI to take up 

 the origin of light in animal bodies. 



Bernoulli's ideas on diffuse sea light will be considered in Chap- 

 ter XV, and his ideas on luminous fish in Chapter XIV. His views 

 on the origin of light in the larger animals sound quite modern. 

 He recognized that many sea animals possessed light organs pro- 

 ducing a " Leuchtstoff " that could be separated without harming 

 the animal and that the light intensity could be controlled by 

 muscular movement, which he thought regulated the admission of 

 air. He held that the light arose during slow burning of an oxidiz- 

 able material which in many cases appeared to be actually phos- 

 phorus. This material was produced by a living process as the result 

 of a vital force,^ and the oxidation came from a supply of air, by 

 respiration or by a similar process. However, the light was not 

 visible during complete but only during incomplete oxidation, and 

 a transparent skin was necessary for detection of internally produced 

 light— no doubt a reference to the transparency of many luminous 

 marine forms such as medusae and ctenophores. Bernoulli actually 

 considered it possible that many animals, frogs for example, might 

 be found to produce light, if they were opened by vivisection. He 

 called attention to the fact that in some forms luminous material 

 could be secreted into a reservoir and then expelled by the contrac- 

 tion of muscles. Such secretions were not necessary for the life of 

 the animal but their purpose was unknown. In contrast to these 

 definite statements his views on the light of dead animal tissues 

 (fish and flesh) were highly imaginative. 



Christoph Bernoulli was one of the famous Bernoulli family, 

 whose scientific contributions started with the brothers Jacob I 

 (1654-1705) and Johann I (1667-1748) , the great mathematicians 

 of Basel. Johann II (1710-1790), youngest son of Johann I, pro- 

 fessor of rhetoric and also mathematician at Basel, had a son Daniel 

 II (1751-1834) , an M. D. and a professor of rhetoric at Basel, who 

 was the father of Christoph. His thesis, Ueber das Leuchten des 

 Meeres (Gottingen, 1803) , was his only work concerned with lumi- 

 nescence. Later publications dealt with anthropology, mineralogy, 



' Wohler's synthesis of urea, which shattered the idea that biological substances 

 were synthesized by vital force, was made in 1828. 



