a Comparison lelween Animal and Vegelalle Life. 97 



water ; nor do they open them in the morning till the sun has 

 power enough to decompose the licpiid. Then what clouds of 

 apparent smoke pour from every hedge or tree, filling the morn- 

 ing air with vapour ! 1 doubt not also that much of this pure 

 gas is given out when tlie leaf forms its pabulum, from the de- 

 composition of the several juices the hairs have collected to com- 

 pose thlc nev compound, in which all vital air is banished. Nor 

 is it iujj'robuMe that the hairy points mayheln^n a bright day to 

 decompose and set at liberty the oxygen of Voz ubbles of water 

 without further process, as it certainly occur' ; the green mat- 

 ter 0'- frefih. water covferva in Priestley's expeiiment, which is 

 owing to the fine points of both. As those insects which have 

 spiracula or breathing apertures, as wasps and flies, are imme- 

 diately suffocated if oil be poured on them, so the leaves (if a brush 

 is merely passed over them, giving tliem a simple varnish of oil) 

 directly ^roM^ black and die. The confining tl}e air within them, 

 and stopping all their natural functions, is sufficient to kill them. 

 That some thick flowers serve as respiratory organs as well as 

 the leaves, I have no doubt, since there are in most of them open 

 air-vesselt for the purpose : when without leaves, therefore, the 

 petals serve as lungs to the plant, as they always have that cir- 

 cular vessel alternately holdii,^- air or water surrounding them, 



A tree in the winter will bear the closest confinement; but the 

 moment its leaves appear and open, if it has not plenty of air it 

 dies: hence the number killed in a hot day in spring. Nothing 

 can be more different than the skin of a human being and the 

 cuticle of a plant: in one point only they agree — that they have 

 both many layers. The human ciilis which covers the flesh is 

 composed ofjidres closely compacted, through which the ends of 

 the nerves appear which give out perspiration, and on which skin 

 innumerable papillce are discovered coiled up, or spread out, and 

 which seem to be calculated to receive the impressions of thetouch, 

 being the most in quantity where the sense of feeling is the most 

 delicate, as in the palms of the hands and the fingers. This 

 skin which will stretch to any extent and contract again, has 

 been known in cases of dropsy to stretch a foot or two, and re- 

 duce itself when the water was discharged. It is always of a 

 white colour, while the matter which covers it and lies between 

 the cutis and epidermis is that which gives the tint to the fair, 

 brown, or black person. This is called the rete mucosurn ; it is 

 a mucous substance which may be dissolved in water, and which 

 mnegroes is quite lta(k. Next to this is the epidermis or scarf 

 skin. It is a fine transparent insensible ptZ/ic/c, destitute of nerves 

 and blood-vessels, and every where covering the true skin, which 

 /nvests the body. It is in reality composed of several laminae or 

 lif-ales, and is full of pores, through which the perspiration passes 



Vol. 4G. No. 208. August 1 8 i 5 . G from 



