ATO 



ATR 



experiments of Mr. Davy, there appears 

 to be a consumption of a very small por- 

 tion of its nitrogen. Atmospheric air is 

 very sparingly absorbed by water ; and 

 the aborption is unequal, more of the 

 oxygen being combined with the water 

 than of the nitrogen. It is difficult, even 

 by long boiling, to expel from water the 

 whole of the oxygen which it holds dis- 

 solved; and if exposed again to the at- 

 mosphere, it very quickly imbibes it. 



Atmospheric air is an important agent 

 in many of the operations of nature. Be- 

 sides serving as the vehicle of the distri- 

 bution of water, it is, by its mobility, the 

 great agent by which temperature is in 

 some measure equalized, or at least its 

 extremes moderated. Animals, as we 

 have seen, are dependent on it for life. 

 It is essential to respiration ; in the more 

 perfect animals, its deprivation cannot be 

 sustained for a few moments ; and even 

 in the less perfect, the abstraction of it is 

 followed, though not so immediately, by 

 death. Its agency depends chiefly on its 

 oxygen, a quantity of which is spent in 

 every inspiration in produing chemical 

 changes in the blood. A part of its ni- 

 trogen also is consumed, while a portion 

 of carbonic acid gas is formed and ex- 

 pired. Vegetable life is also in part de- 

 pendent on it ; it conveys water and per- 

 haps carbonic acid gas, and other princi- 

 ples, to the leaves of plants, and is thus 

 subservient to their nutrition and growth. 



ATO MIC ALphilosophy denotes the doc- 

 trine of atoms, or a method of accounting 

 for the origin and formation of all things 

 from the supposition of atoms endued 

 with gravity and motion. The atomic 

 physiology,accordingtothe account given 

 of it by Dr. Ctidworth, supposes that bo- 

 dy is nothing else but an extended bulk; 

 and resolves, therefore, that nothing is to 

 be attributed to it but what is included 

 in the nature and idea of it, viz. more or 

 less magnitude, with divisibility into parts, 

 figure, and position, together with mo- 

 tion or rest ; but so as that no part of 

 body can ever move itself, but is always 

 moved by something else. And conse- 

 quently it supposes that there is no need 

 of any tiling else besides the simple ele- 

 ments of magnitude, figure, site and mo- 

 tion, which are all clearly intelligible, as 

 different modes of extending substance to 

 solve tlie corporeal phenomena by ; and, 

 therefore, not of any substantial forms 

 distinct from the matter, nor of any other 

 qualities really existing in the bodies 

 without, besides the results or aggre- 

 gates of those simple elements, and the 



VOL. U. 



disposition of the insensible parts of bo- 

 dies, in respect to figure, site, and mo- 

 tion, nor of any intentional species or 

 shews, propagated from the object to ouF 

 senses ; nor, lastly, of any other kind of 

 motion or action really distinct from local 

 motion, such as generation and alteration, 

 they being neither intelligible as modes 

 of extended substance, nor any ways ne- 

 cessary. Forasmuch as the forms and qua- 

 lities of bodies may well be conceived to 

 be nothing but the result of those simple 

 elements of magnitude, figure, site, and 

 motion, variously combined together, in 

 the same manner as syllables and words, 

 in great variety, result from the different 

 combinations and conjunctions of a few 

 letters, or the simple elements of speech ; 

 and the corporeal part of sensation, par- 

 ticularly that of vision, may be solved on- 

 ly by local motion of bodies, that is, either 

 by corporeal effluvia streaming continu- 

 ally from the surface of the objects, or 

 rather, as the latter and more refined atom- 

 ists conceived, by pressure made from 

 the object to the eye, by means of light 

 in the medium. So that the sense taking 

 cognizance of the object by the subtle 

 interposed medium, that is tense and 

 stretched, (thrusting every way from it 

 upon the optic nerves) doth by that, as 

 it were by a staff, touch it. Again, gene- 

 ration and corruption may be sufficiently 

 explained by concretion and secretion, or 

 local motion, without substantial forms 

 and qualities. And, lastly, those sensible 

 ideas of light and colours, heat and cold, 

 sweet and bitter, as they are distinct 

 things from the figure, site, and motion of 

 the insensible parts of bodies, seem plain- 

 ly to be nothing else but our own fancies, 

 passions, and sensations, however they 

 be vulgarly mistaken for qualities in the 

 bodies without us- 



ATRA bills, in ancient medicine, the 

 black bile, one of the humours of the an- 

 cient physicians, which the moderns call 

 melancholy. Dr. Percival suggests that 

 this disorder is occasioned by the stagna- 

 tion of the gall, by which it is rendered 

 too viscid by the absorption of its fluid 

 parts. Bile in this state discharged into 

 the duodenum occasions universal distur- 

 bance, until it be evacuated. It brings on 

 vomiting, purging, &.c. previous to which, 

 are fever, delirium, &c. 



ATRACTYLIS, in botany, a genus of 

 the Syngenesia Poly garoia class of plants, 

 with radiated flowers and compressed 

 seeds, coronated with a plumose down, 

 and standing on a plane villose receptacle. 

 There are eight species, of which we may 



M 



