_ ash united to two particles of sulphuric acid. 
| of another, and so on. 
ATRAGENE. 
proportions in which they combine, are multiples 
of some simple number representing the jirst. 
This law of multiple proportions was discovered 
or detected by Mr. Higgins of Dublin, about the 
year 1789; and it is upon this view of combina- 
tion that Mr. Dalton founded his atomde theory, 
in which, assuming the existence of ultimate pon- 
derable atoms, he regards these atoms as meet- 
ing or combining with each other aecording to 
definite laws of multiple proportion. According 
to this theory, bodies unite either atom to 
atom, or two or three atoms of one to one 
atom of another. Thus water is composed of 
an atom of oxygen and an atom of hydrogen 
united together ; ammonia of an atom of hydro- 
gen and an atom of azote united together; car- 
bonic acid of two atoms of oxygen united to one 
of carbon. Sulphate of potash consists of a par- 
ticle of sulphuric acid united to a particle of pot- 
ash ; supersulphate of potash of a particle of pot- 
If 
we admit that matter is composed of atoms, as 
is at least probable, it is difficult to refuse admis- 
sion to this hypothesis, though it is probable that 
more complicated cases may exist. For example, 
two atoms of one body may combine with three 
It is even possible that 
the proportion in which bodies unite cannot al- 
ways be represented by numbers. But this hy- 
pothesis of Dalton is much more probable, and 
| corresponds much better with the phenomena, 
than the opposite one of Berthollet, that bodies 
combine in all proportions whatever. Dalton’s 
hypothesis is very useful, because it facilitates 
the knowledge of the composition of bodies. For 
example, if water be composed of an atom of hy- 
drogen and an atom of oxygen, it follows, from 
the known analysis of water, that the weight of 
' an atom of hydrogen is to that of an atom of 
oxygen as 1 to 6. Hence we know, that when 
oxygen enters into a combination, it will always 
enter as 6, or as some multiple of 6. This is very 
observable in the metallic oxides. The quantity 
of oxygen in the second oxide is usually double 
that in the first oxide, and that in the third 
triple that in the first. The same thing is equally 
remarkable in the salts; the supersulphate of 
potash contains just double the quantity of sul- 
phuric acid that exists in the sulphate, and all 
the supersalts contain twice as much acid as the 
neutral salts, with the same acid and base. Mr. 
Dalton assumed hydrogen as the unit or radix of 
his scale, on account of its being the lightest body 
in nature, as combining in the smallest propor- 
tions, and, consequently, as tending to a series of 
numbers which, for all other bodies, are multi- 
ples of itself. Wollaston and Berzelius, however, 
prefer oxygen as a radix, on account of its uni- 
versal agency, and very frequent occurrence in 
compounds, 
ATRAGE’NE. A genus of ornamental, hardy, 
| perennial, herbaceous climbing plants, of the ra- 
nunculus tribe, recently separated from the large 
ATROPHY. 291 
and well known genus clematis. Five species, from 
Siberia, Austria, and North America, are culti- 
vated in Britain, and grow to the height of from 
ATROPA. <A genus of very poisonous plants, 
of the nightshade or potato family. The princi- 
pal species is the belladonna or deadly night- 
shade, a perennial herb, growing wild upon ac- 
cumulations of rubbish in Great Britain, and 
well known for both its fearfully poisonous na- 
ture, and its modern extensive use in medicine, 
particularly in homeopathy. See the article 
Bretiaponna. The only other species growing in 
Great Britain is Atropa arborescens, a tender, 
evergreen shrub, with white flowers, and a height 
of 15 feet, introduced from Jamaica in 1833. 
But about a dozen other species have been de- 
scribed by botanists. 
ATROPHY. A wasting away of flesh and 
strength in animals, caused or accompanied by 
inability of the digestive and absorbing organs 
to extract sufficient nourishment for food. There 
are many diseases in which the body becomes 
daily more lean and emaciated, appears deprived 
of its common nourishment, and, for that reason, 
of its common strength. It is only, therefore, in 
those cases in which the emaciation constantly | 
increases, that it constitutes a peculiar disease ; | 
for when it is merely a symptom of other com- | 
mon diseases, it ceases with the disease, as being 
merely a consequence of great evacuations, or of 
the diminished usefulness or imperfect digestion 
of the nourishment received. But, when ema- 
clation or atrophy constitutes a disease by itself, 
it depends upon causes peculiar to this state of 
the system. These causes are, permanent, op- 
pressive, and exhausting passions, organic dis- 
ease, a want of proper food or of pure air, ex- 
hausting diseases, as nervous or malignant fevers, 
suppurations in important organs, as the lungs, 
the liver, &c. Copious evacuations of blood, 
saliva, semen, &c., are also apt to produce this 
disease, and, on this account, lying-in women, | 
and nurses who are of slender constitution, and 
those who are too much addicted to venery, are 
often the subjects of this complaint. This state 
of the system is also sometimes produced by poi- | 
sons, e. g., arsenic, mercury, lead, in miners, 
painters, gilders, &c. A species of atrophy takes 
place in old people, in whom an entire loss of | 
strength and flesh brings on a termination of | 
life without the occurrence of any positive dis- | 
order. It is known as the Marasmus senilis, or | | 
atrophy of old people. Atrophy is of frequent 
occurrence, in infancy, as a consequence of im- 
proper, unwholesome food, exposure to cold, 
damp, or impure air, &c., producing a super- 
abundance of mucus in the bowels, worms, ob- 
structions of the mesenteric glands, followed by 
extreme emaciation, which state of things is 
often fatal, although the efforts of the physician 
are sometimes successful, when all the causes of 
8 to 15 feet. 
ATRIPLEX. See OracuHeE. : 
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