136 ANIMAL. 



one of the products of the laws of vitality with engendering heat, and of regulating their own 



the essence of which we are altogether un- temperature : this faculty, however, and the 



acquainted. degree of heat they possess at different times, 



are influenced to a very considerable degree by 



Besides the secretion of the various gaseous, the heat of the media in which they live. The 



fluid and solid matters mentioned, vegetables same statements may be made with regard to 



and animals appear in common to possess the fishes. The temperature of these creatures is 



power of disengaging certain imponderable generally several degrees above that of the water 



elements heat, light, and electricity. they inhabit; but it also varies with the tem- 



Heat. There has been considerable variety perature of their native element, 



of opinion among physiologists with regard to Many insects have a very decided power of 



the extent to which vegetables have the power engendering heat and of regulating their tem- 



of maintaining a temperature of their own hide- perature; and similar faculties have been de- 



pendently of that of the surrounding media, monstrated in the Crustacea, the mollusca, and 



Nor is this question, in our opinion, yet com- the annelida. These tribes, however, are all 



pletely set at rest. It is certain that trees in very much influenced by the temperature of the 



high northern latitudes endure a cold many de- media surrounded by which they live, 



grees below zero without injury, whilst in in- No great difference is therefore discernible 



tertropical countries they are frequently ex- between vegetables and animals in the faculties 



posed even in the shade to a heat above that they possess of engendering caloric and regu- 



of any animal without perishing ; actual ex- lating their own temperature ; the faculty is 



periment, indeed, proves that they preserve a only much more decided, and possessed to a 



temperature intermediate between that of the far greater extent among the more perfect 



extreme heat and extreme cold of the diurnal classes of animals generally than among vege- 



variations of those latitudes in which they are tables at large. It may very fairly, in the 



indigenous. This circumstance is explained present state of our knowledge, be ascribed as 



variously, some attributing it to a vital property a common property. 



in plants to regulate to a certain extent their As to the mode in which heat is engendered, 



own temperature, others alleging that it is opinions are still very much divided. The 



merely owing to the indifferent conducting chemical and mechanical explanations that 



qualities of the materials of which vegetables have been given of the phenomenon are not 



are composed. The thermometer has been seen universally applicable. All we can say at the 



several degrees below the freezing point of present day is that the production of heat and 



water within the trunks of fir trees, without the power of regulating their temperature pos- 



their vitality being affected ; but it is probable sessed by organized beings is another of the 



that the constitution of this tribe renders them hidden and singular law r s or properties intro- 



capable of enduring such a reduction of tern- duced into the system of the universe with their 



perature with impunity as would prove fatal to creation. 



other trees with simple watery sap. Light. Many unorganized bodies have the 



On the other hand, it is quite certain that the property of shining or giving out light for some 



flowers of many vegetables have the power of time after they have been exposed to the bright 



disengaging heat, a difference of ten, twenty, rays of the sun, or have been heated in the fire, 



and even more than thirty degrees having been or when they are struck together or smartly 



observed at sun-rise between the temperature compressed, and this certainly without any 



of the atmosphere and that of the flowers of decomposition of their substance. The disen- 



different vegetables in southern latitudes, and gagement of light, again, is a very uniform 



the same thing is known to occur, though to a accompaniment of the decomposition and com- 



less extent, in northern countries. position of inorganic substances, and it appears 



It would therefore be unfair, with such facts to be a very constant attendant upon electrical 



before us, to deny altogether to vegetables the phenomena. 



faculty of disengaging caloric. Arguments, in- Various organic substances and products of 



deed, a priori, might be adduced to show that organization have a similar property ; living 



they must almost necessarily possess such a vegetables, too, particularly the flowers, have 



property : they are the subjects of incessant been seen to give out light by authorities so 



change; and one of the most universal of the respectable, that though the fact has been 



physical laws involves a change of temperature called in question by others of great name, 



on any change of constitution. there seems no sufficient reason for treating all 



If the faculty of vegetables generally to that has been said on the subject as illusion : 



secrete or eliminate caloric be doubtful, how- in the physical sciences negatives cannot be 



ever, it is indisputable that among all animals received as evidence of equal value with posi- 



a little raised above those at the very bottom of tives. 



the scale, there is an inherent power of gene- No one thinks of calling in question the 

 rating caloric, which in their state of maturity luminousness of animals ; most of the innu- 

 is nearly determinate as regards each particular merable inferior tribes that live in the sea, 

 species. Mammalia and birds have universally appear to possess and to manifest this pro- 

 the highest temperatures. perty at different seasons. The luminous- 

 Reptiles or cold-blooded animals, as they ness of the ocean itself, so familiarly known, 

 are improperly called, have also the power of seems to depend o'n the presence of multitudes 



