Chemical Science. IS\ 



over the wound of an officer, who had been dressed with com- 

 presses wetted with pure water only. Baron Percy has since 

 had frequent opportunities of observing similar facts. 



14. On the Phosphorescence of luminous Insects. — This subject 

 is treated by M. Macair in a Memoir published in the Bibl. Uni- 

 vers. 1821. The insects on which his experiments were princi- 

 pally made, were the Lampyrus noctiluca and splendidula, known 

 by the common name of glow-worms. The following are some 

 of the general and striking results. 



Solar light appears to have a constant influence on these 

 animals. Some were put into boxes, from which the light was 

 shut out, and when the boxes were opened in the evening, they 

 rarely gave any light; but the same worms, in the same boxes with 

 glass tops, and placed in the sunshine, shone brilliantly in the 

 ensuing evening. 



Heat caused these animals to become luminous, and they re- 

 mained so as long as the heat was continued ; it began at 22° R. 

 was brightest at 33° R., the insect then soon died, but the light 

 continued ; at 46° it ceased. When the animals were thrown 

 into water of 35° or 40°, they died instantly, but the light con- 

 tinued brilliant: at 10° higher all light was extinguished, and 

 could not be restored. Cold, on the contrary, destroys the 

 luminousness of the insect. 



When the luminous part of the animal is cut off, the light dir 

 minishes, and in four or five minutes is gone. In a few minutes 

 the rings move and the light re-appears, but more weakly, and 

 then fades away. This continues two or three days, but the light 

 is faint; if the part be warmed, then the light is brilliant, and 

 by renewing it may be restored for two or three days together as 

 often as is desired. 



When the abdomen of a worm is opened the luminous matter 

 is found within, formed by a particular organization. It appears 

 as a yellowish white matter on the last three rings semi-trans- 

 parent, which in the microscope appears organized, and coiisist- 

 ing of grains confined in a ramifying fibrile structure, shining 

 brightly in the dark. The interior surface of the ring is very 

 transpaicnt, but not phosphorescent. The substance is trans- 

 lucid, becomes opaque by drying, and then ceases to shine. It 

 is heavier than water. Preserved openly in water it shines with 

 a yellowish-green light for two or three hours, and then ceases 

 shining. Heat and galvanism reproduce the light as long as the 

 substance is not quite opaque. Up to 33° R. the light increases ; 

 at 42° it ceases, and the substance is then white and opaque like 

 albumen. In a vacuum it ceases to shine, but reshines with air. 

 it shines more in oxygen than in other gases. When burned it 

 gives ammonicul results. Concentrated acids extinguish the 

 light and coagulate the substance. It is not soluble in oils. 

 Ether and alcohol destroy the light, and coagulate the sub- 



