LYMPHATIC AND LACTEAL SYSTEM. 



205 



the emission of light from the eyes of some 

 animals, independently of the reflexion of in- 

 cident light. The ape in question is nocturnal. 

 The luminousness of the eye was seen by 

 Rengger only when there was total darkness ; 

 and then the light was so brilliant that objects 

 at the distance of a foot and a half from the 

 eye were distinctly seen.* In commenting on 

 this statement by Rengger, Treviranus remarks,t 

 " that the intensity of light may be increased 

 by the brilliant tapetum of the eye, while it is 

 concentrated as in a concave mirror, cannot be 

 doubted. But it is impossible that a feeble 

 light so concentrated should illuminate objects 

 placed at the distance of a foot and a half from 

 the eye of this ape, in a dark place." The 

 same physiologist seems to be satisfied that 

 some dogs also have a similar power of gene- 

 rating light within their eyes. In these, he 

 states, the light is seen only when an impres- 

 sion on the sight or hearing arouses the ani- 

 mal's attention, or when he is excited by the 

 operation of some instinct or passion. 



We are, therefore, constrained to conclude 

 that this subject is still open for elucidation by 

 future inquirers. If it should be proved that 

 some of the higher animals really do emit 

 light from their eyes, independently of the in- 

 cidence and reflexion of that from without, it 

 will go far to render it probable that, in lumi- 

 nous animals generally, the development of 

 light depends more upon the movements of 

 some imponderable agent in and from their 

 nervous system, than upon the nature of the 

 composition of the fluids poured out by the 

 luminous organs. 



Another series of phenomena, intimately 

 connected with, and illustrative of, those previ- 

 ously considered, demands notice here, namely, 

 the shining of fishes, and other animal bodies 

 shortly after death. The luminousness of dead 

 fishes is a very common subject of observation, 

 but not on that account the less worthy of par- 

 ticular attention. It has been ascertained that 

 the light is given out from every part of the 

 body, external and internal, that is exposed to 

 the air ; and that on the surface of the luminous 

 parts there is a slight moisture, or solution of 

 the tissues of the animal, which can be scraped 

 off, or diffused in water, and continues lumi- 

 nous for a short time after being so removed. 

 When pieces of the skin or muscle of a fish 

 are placed in a little water, the luminousness 

 appears only on the surface when the water is 

 at rest; but whenever it is agitated the light is 

 diffused through the whole body of water. 



In some fishes, as the whiting, this lumi- 

 nousness appears within a very short time after 

 death ; in others, not for some days ; but in 

 all it ceases before the truly putrefactive process 

 has commenced. It is observed that those 

 fishes which most quickly putrefy, are also 

 those which give out light the soonest. 



From the circumstance mentioned above, 

 that this luminous fluid formed on the bodies 

 of dead fishes is miscible with water, and re- 



* Rengger's Naturgesch. der Saugthiere von 

 Paraguay, s. 383. 

 t Biologic, i. 439. 



tains its luminousness for a short time after 

 being so mixed, it has been concluded that the 

 beautiful phenomenon of the phosphorescence 

 of the sea may be frequently owing to the pre- 

 sence, in great quantity, of the remains of fishes 

 recently dead. It is certain that the most 

 careful observers sometimes fail to delect any 

 entire living animals in sea water taken up 

 from a brilliantly luminous sea; and find only 

 abundance of small fibres and shreds of what 

 seem to be broken-down animal tissues. Pro- 

 fessor Smith* concluded from his own obser- 

 vations made in the Atlantic, that, while the 

 bright sparkling light of the surface of the 

 ocean is always emitted by living animals, that 

 duller diffused luminousness, which is fre- 

 quently seen over a vast extent of the sea, 

 giving it the appearance of milk, is given out 

 by " a dissolved slimy matter, which spreads 

 its light like that proceeding from phosphorus." 

 Under the most powerful microscope, Smith 

 saw nothing in such water but " the most mi- 

 nute glittering particles, having the appearance 

 of solid spherules." Humboldt saw a great 

 extent of the surface of the sea rendered almost 

 gelatinous by the admixture of numbers of 

 dead dagyste and medusa. 



It may, therefore, be regarded as probable, 

 at least, that the luminousness of the ocean is 

 sometimes caused by dead matter ; but it is 

 certain that, in the great majority of instances, 

 it is entirely owing to the presence of living 

 animals, possessed of the light-giving property .-f 

 In attempting to examine these, so as to deter- 

 mine their forms and habits, it is important to 

 keep in mind that they are sometimes ex- 

 tremely small, so as to be distinguished with 

 considerable difficulty, even with the aid of the 

 best microscopes. And when they are larger, 

 they are frequently so transparent as to elude 

 notice. 



BIBLIOGRAPHY. Canton, Phil. Trans. 1769. 

 446. Macartney, Phil. Trans. 1810. 2. Spallan- 

 xani, Mem. della Soc. Ital. vii. 271. Macaire, 

 Mem. sur les Lampyres, in Jour, de Physique, 

 xciii. 46. Humboldt, Reise i. 109. Todd, Jour- 

 nal of Science, 18'26. 241. Murray, Experimental 

 researches, 1826. Kirby and Spence, Introd. to en- 

 tomol. ii. 256. Qiwy and Gaimard, Ann. des Sc. 

 Nat. iv. 1. Tiedemann, Comp. pliysiol. i. 257. 

 Macculloch, Phosphorescence, in Edin. Encycl. xvi. 

 1823. Burmeister, Manual of entomol by Shuch~ 

 hard, 494. Muller, Physiology, by Baly, vol. i. 

 ed. 2, 1839. 



LUNG. See PULMONARY ORGANS. 



LYMPHATIC AND LACTEAL SYS- 

 TEM. (Fr. Systeme lymphatique ; Germ. 

 Saugadersystem oder Lyrnphgefdssst/atem. 



* Tuckey's Voyage, 258. 



t Martin, Canton, Hulme, and others supposed 

 the luminousness of the sea to be caused by a phos- 

 phorescent oil, generated during the putrefaction of 

 animals. Silberschlag regarded it as phosphoric. 

 Mayer, Beccaria, Monti, Brugnatelli, and others, 

 believed it to be owing to the giving out of light 

 imbibed from the sun's rays. Bajon, Delaperriere, 

 and Gentil imputed it to electrical agency, because 

 it is excited by friction. Foster supposed it to be 

 sometimes electric, and sometimes putrefactive. 



