640 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



Epsom salt, Glauber's salt, sea-salt, and sal ammonia: if either of the 2 former 

 be used, the proper proportion is, 1 dr. of salt to each oz of water ; if either of 

 the 2 latter, 1 5 gr. to each oz. of water will be sufficient. 



n. b. The experimentalist, before he views the descent of the light in the tube, 

 should always remain in the dark for some little time, in order to get rid of all ex- 

 traneous light adhering to the organs of vision, and to accommodate the eye to 

 darkness. 



Section 10. The Effects of the Human Body, and of the Animal Fluids, on 



Spontaneous Light. 



The living Body. — Exper. 1 . On touching the luminous matter of fishes, the 

 light adhered to the fingers and different parts of the hands; remained very lucid 

 for some little time, and then gradually disappeared. But the same kind of matter 

 being applied to pieces of wood, stone, and the like, of the same temperature as 

 the laboratory, continued luminous on these substances for many hours. — Exper. 2. 

 A piece of red blotting-paper, about 1 inch square, and 4 times doubled, was 

 finely illuminated by matter from a herring, and applied to the upper part of the 

 inside of the thigh. After the expiration of 1 5 or 20 minutea, it was taken off; 

 when the light was quite extinguished. The experiment was repeated several times, 

 and with the same effect. Another piece of the like paper was illuminated at the 

 same time, and placed in the laboratory ; where it retained its light above 48 hours. — 

 Exper. 3. A piece of shining wood was placed on the palm of the hand, and in- 

 closed there for some time; on inspection, it was found to be more lucid than 

 before. Many trials of this kind were made, with the like success. — Exper. 4. A 

 dead glow-worm, being but slightly luminous, was breathed on several times; and 

 its light increased both in magnitude and brightness. The experiment was fre- 

 quently repeated, with the same result. 



minimal Fluids. — Blood. Exper. 5. A person having received a contusion, but 

 otherwise in health, was bled. The next day some herring-light was mixed with 

 about 2 oz. of the crassamentum or red coagulated part of the blood, by stirring 

 them well together with a knife: it caused it to be slightly luminous, but the light 

 was not of long duration. Nearly the same result followed the mixture of lucid 

 matter with the recent crassamentum of persons labouring under inflammatory 

 diseases, as the pleurisy and rheumatism. — Exper. 6. But when mixed with cras- 

 samentum that had been kept for some time, and become black and somewhat 

 offensive to the smell, the light seemed to be more quickly extinguished. — Exper. 7. 

 A singular phenomenon happened several times, on mixing fish-light with pru- 

 trescent bloody serum. It would not incorporate, but was ejected in globules, like 

 quicksilver when rubbed with any unctuous substance, and afterwards adhered to 

 the side of the vessel in which the mixture was made, in the form of a lucid ring. — 

 Exper. 8. The luminous matter of a herring was mixed with about 2 oz. of pure 

 serum, from the healthy subject of the 5th experiment: it soon became finely il- 

 luminated, and retained its shining appearance for a long time, whenever it was 



