HEALING OF OPEN WOUNDS. 327 



material is rapidly developed into cells, amongst which, blood- 

 vessels speedily extend themselves. The formation of new 

 blood-vessels, in this and other cases, seems to commence in 

 the giving- way of the walls of some of the previously-existing 

 capillary loops, at particular spots, and in the escape of blood 

 corpuscles in rows or files into the soft substance that sur- 

 rounds them ; thus channels or passages are excavated, which 

 come into connexion with each other; and these channels, 

 after a time, acquire proper walls, and become continuous 

 with the vessels from which they originated, to be in their 

 turn the originators of a new series. The vitality of this new 

 " granulation- tissue," however, is very low; and the part ex- 

 posed to the air passes into the condition of pus (the yellow 

 creamy fluid discharged from an open wound), which contains 

 the same materials in a decomposing state. Thus there is a 

 constant waste of organizable substance, the amount of which, 

 in the case of an extensive wound, becomes a serious drain 

 upon the system ; at the same time, there is a much greater 

 irritative disturbance both in the part itself and in the system 

 generally ; and the new tissue that is formed is of such low 

 vitality that it subsequently wastes away, so as by its disap- 

 pearance to leave a contracted cicatrix or scar. The difference 

 between the two modes of reparation now described is often 

 one of life and death, especially in the case of large burns of 

 the body in children. 



CHAPTEE IX. 



ON THE EVOLUTION OP LIGHT, HEAT, AND ELECTRICITY BY ANIMALS. 



Animal Luminousness 



394 A large proportion of the lower classes of aquatic 

 Animals possess, in a greater or less degree, the power of 

 emitting light. The phosphorescence of the sea, which has 

 been observed in every zone, but more remarkably between 

 the tropics, is due to this cause. "When a vessel ploughs the 

 ocean during the night, the waves especially those in her 

 wake, or those which have beaten against her sides exhibit 

 a diffused lustre, interspersed here and there by stars or 

 ribands of more intense brilliancy. The uniform diffused 



