32 
hatched without feathers, and of certain animals 
which are born blind; and in hybernation it is 
almost extinct. 
To ascertain the quantity of respiration in 
apy given animal, with extreme minuteness, 
was a task of great difficulty. It was still 
more difficult to determine this problem, so as 
to represent the quantities of respiration in the 
different kinds, ages, and states of animals, in 
an accurate series of numbers. The changes 
induced in a given volume of air made the 
subject of experiment, by changes in the tem- 
ature and pressure of the atmosphere, and 
y variations in the height of the fluid of a 
pneumatic trough, which it is so difficult to 
appreciate minutely; the similar changes in- 
duced by the humidity of expired air, and by 
the heat of the animal itself, were so many 
and complicated, that it appeared almost im- 
man to arrive at a precise result. These 
ifficulties, in fine, were such as to lead one of 
the first chemists of the present day to give up 
some similar inquiries in despair. 
Fortunately I have been enabled to devise 
an apparatus which reduces this complex pro- 
blem to the utmost degree of simplicity. I 
now beg the indulgence of the reader whilst 
I give a detailed description of its construction 
and mode of operation. 
Fig. 1. 
(ara 
IRRITABILITY. 
This apparatus, which I shall designate th 
pneumatometer, consists of a glass jar (fig. * 
a, b,) inverted in a mercurial trough (c, d,) s 
grooved and excavated, as accurately to receiv 
the lower rim of the jar and the lowest pai 
the tube (e, f, g,) and also to admit of the an 
mal which is made the subject of experimer 
being withdrawn through the mercury. Th 
jar communicates, by means of the bent tub 
(e,f, g,h,) with the gauge (i, j,) which is i 
serted into a larger tube (k, /,) containing wate 
A free communication between the jar and t 
external air is effected and cut off, at a 
by introducing and withdrawing the little be 
tube (m,n,) placing the finger upon the € 
tremity (m,) whilst the extremity (m) is passet 
through the mercury. . 
If the jar be of the capacity of one hy 
dred cubic inches, the gauge is to contain t 
and to be graduated into cubic inches a 
tenths of a cubic inch; so that each smalles 
division shall be the thousandth part of th 
whole contents of the jar. x 
Attached to the same vray Hl 
laced a little apparatus (0, p, al 
poseaven and conaisiiat of a glass ball ( 
of the capacity of ten cubie inches, comm 
nicating with a tube (p,g,) bent at its uppé 
part, of the capacity of one cubic inch, ¢ 
GS I’ 
a 
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PERU LITTTTTTPE Terry rrr ryt 
° 
