RESPIRATION, AND x ANIMALIZATION. 145 



carbonic acid gas, by the matter of light, which he supposes to be introduced 

 into the system in the act of respiration, instead of the matter of caloric ; in 

 consequence of which it immediately becomes a pigment. But the difficulties 

 which attend this theory are almost, if not altogether, as numerous as those 

 which attend the theory of combustion, and it is unnecessary to pursue the 

 subject any farther. 



In the Philosophical Transactions, and in several of the best established 

 foreign Memoirs, we meet with a few very curious instances of spontaneous 

 inflammation, or active combustion, having occurred in the human body. 

 The accident has usually been detected by the penetrating smell of burning 

 and sooty films, which have diffused themselves to a considerable distance ; 

 and the sufferers have in every instance been discovered dead, with the body 

 more or less completely burnt up, and containing in the burnt parts nothing 

 more than an oily, sooty, extremely fetid, and crumbly matter. In one or two 

 instances there has appeared, when the ifght was totally excluded, a faint 

 lambent flame bickering over the limbs ; but the general combustion was so 

 feeble, that the chairs and other furniture of the room within the reach of the 

 burning body have in no instance been found more than scorched, and in 

 most instances altogether uninjured. 



It is by no means easy to explain these extraordinary facts ; but they have 

 been too frequent, and are too well authenticated in different countries, to 

 justify our disbelief. In every instance but one the subjects have been females, 

 somewhat advanced in life, and apparently much addicted to spirituous 

 liquors. 1 shall hence only observe, in few words, that the animal body in 

 itself consists of a variety of combustible materials; and that the process of 

 respiration (though not completely established to be such) has a very near 

 alliance to that of combustion itself: that the usual heat of the blood, taking that 

 of man as our standard, is 98 of Fahrenheit, and under an inflammatory tem- 

 perament may be 103 or 104 ; and hence, though by no means sufficiently 

 exalted for open or manifest combustion, may be more than sufficiently so 

 for a slow or smothered combustion ; since the combustion of a dung-hill sel- 

 dom exceeds 81, and is not often found higher in fermenting haystacks, 

 when they first burst forth into flame. The use of ardent spirits may possi- 

 bly, in the cases before us, have predisposed the system to so extraordinary 

 an accident; though we all know that this is not a common result of such 

 a habit, mischievous as it is in other respects. The lambent flame emitted 

 from the body is probably phosphorescent, and hence little likely to set fire to 

 the surrounding furniture. It is not certain whether this flame originates 

 spontaneously, or is only spontaneously continued, after having been pro- 

 duced by a lighted substance coining too nearly in contact with a body thus 

 surcharged with inflammable materials. 



Such, then, are the circulatory and respiratory systems in the most perfect 

 animals ; as mammals, birds, and amphibials. It should be observed, how- 

 ever, that in birds the hollow bones themselves, and a variety of air-cells that 

 are connected with them, constitute, as we have already had occasion to no- 

 tice,* a part of the general respiratory organ, and endow them with that 

 levity of form which so peculiarly characterizes them, and which is so skil- 

 fully adapted to their intention. It should be remarked, also, that in most am- 

 phibious animals, and especially in the turtle, whose interior structure is the 

 most perfect of the entire class, the two ventricles, or larger cavities of the, 

 heart, communicate something after the manner in which they do in the hu- 

 man foetus. The lungs of this class are for the most part unusually large ; 

 and they have a power of extracting oxygen from water as well as from air; 

 whence their capability of existing in both elements. The oxygen, hovv- 

 *3vr?. obtained from the water is not by a decomposition of the water into its 

 sl^"nentary parts, but only by a separation of such air as is loosely combined 

 w*h it; for if water be deprived of air or oxygen, the animal soon expires. 

 V>'e have already observed that some amphibials appear to possess only a 

 single heart, and even that of a very simple structure. 



* Scries i. Lecture xi. p. 118. K 



