34 
irritability; whilst, on the other hand, he 
makes statements which appear to me at va- 
riance with this very opimon. In the Ana- 
tomie Comparée (tome i. p. 49,) this cele- 
brated writer observes, “ Les expériences 
modernes ont montré qu’un des principaux 
usages de la respiration est de ranimer la force 
musculaire, en rendant a la fibre son irrita- 
bilité epuisée.” See also tome iv. p. 301. 
Similar observations are made in M. Cuvier’s 
more recent work, the Régne Animal: “ C’est 
de la respiration que les fibres musculaires 
tirent l'énergie de leur irritabilité,” (tome i. 
p- 57, 2me edit.) “ C’est la respiration qui 
donne au sang sa chaleur, et a la fibre la sus- 
ceptibilité pour l’irritation nerveuse,” (tome ii. 
p-1.) On the other hand, a’ of the 
mollusca, (tome iii. P; 3,) M. Cuvier observes 
of those animals of low respiration, * L’irri- 
tabilité est extreme dans la plupart.” The 
same term is, in fact, used in two distinct 
senses, in these paragraphs. 
No further proof can be necessary of the 
extreme vagueness and incorrectness of the 
revailing notions and expressions of physio- 
Aaiate in regard to this subject. All this will 
appear still more extraordinary, when the 
law, that the quantity of respiration and the 
degree of the irritability are, in fact, inverse 
throughout all the series, stages, and states of 
animated being, is clearly established. 
It is well known that the irritability of the 
heart and of the muscular fibre in general is 
greater in the mammalia than in birds, and in 
reptiles and amphibia than in the mammalia, 
whether we judge of it by the force and dura- 
tion of the beat of the heart, exposed to the 
stimulus of the atmospheric air, or by the con- 
tractions of the other parts of the muscular 
system. Now this is precisely the order of the 
quantity of respiration in these animals, as 
ascertained by the pneumatomer, inverted. It 
is essential, in accurately determining the ques- 
tion of the irritability of the muscular fibre, to 
compare animals of the same class inter se; 
birds and the mammalia, reptiles and amphibia, 
fishes, the mollusca, &c. must be compared 
with each other, both generically and specifi- 
cally. It is especially necessary to compare 
the warm-blooded, the cold-blooded, the air- 
breathers, and the water-breathers, in this man- 
ner. However the different classes may differ 
from each other, there are differences in some 
of the species of the same class, and especially 
that of fishes, scarcely less remarkable. 
Great differences in the duration of the beat 
of the heart are observed in feetal, early, and 
adult states of the higher animals; this dura- 
tion being greater in the first, and least in the 
last of these conditions. The order of the 
quantity of respiration is inverse. 
The law of the irritability being inversely as 
the respiration, obtains even in the two sides of 
the heart itself, in the higher classes of animals. 
The beat of the heart removed from the body 
does not cease at the same time in the wall of 
all its cavities, or of its two sides: but, as 
Harvey observes, “ primus desinit pulsare 
sinister ventriculus ; deinde ejus auricula; de- 
IRRITABILITY. 
mum dexter ventriculus ; ultimo (quod etiam 
notavit Galenus) reliquis omnibus cessantibt 
et mortuis, pulsat usque dextra auricula.”* — 
Even in this case the irritability is greatest i 
the part in which the respiration is least. _ 
It was shown by Hook, in the early days o 
the Royal Society,t that if, the iration 
being suspended, an animal appeared to 
dying, the beat of the heart and the signs 
life were speedily restored, on performing art 
ficial respiration, or even by forcing air throu 
the trachea, bronchia, and pulmonary ait-e 
and allowing it to escape through incision 
made through the pleura. ‘ 
It was, in the next place, clearly shown b 
Goodwyn, in one of the most beautiful spe 
cimens of physiological inquiry in any lan 
guage,} that in suspended respiration, it is th 
left side of the heart which first ceases t 
contract, the right side still continuing it 
function for several minutes, until the suppl, 
of blood may be supposed to fail. 
The facts detailed by Harvey had shown tha 
the left side of the heart was endued with le: 
irritability than the right; the experiment ¢ 
Hook, that respiration restored the action ¢ 
the heart, if it had previously ceased ; that 
Goodwyn, that this cessation and restorati 
of functions were observed in the left side ¢ 
the heart. It was obvious, on the other ham 
that the respiration belongs, as it were, to th 
left side of the heart. ‘ 
It appears plainly deducible from these fact 
that in circumstances and structures the mos 
similar, the respiration is accurately inve 
as the irritability. 7 
For the sake of a comparison with the hy 
bernating animal, the object of which will 
explained hereafter, I thought it right to repe 
this experiment. : 
Before I proceed to detail the result, I ma 
just describe an easy method o 
that part of it which consists of artificial res: 
ration. A quill is firmly fixed in the divide 
trachea: a small hole is then cut into that pat 
of the quill which is external; Read’s syring 
is then adapted to the other end of the qi 
At each motion of the piston downwards, - 
lungs are distended ; whilst the piston is raise 
the air escapes through the opening in the qu 
peasneing expiration. The experiment, thei 
ore, only requires the common action ¢ 
syringe. 
The experiment itself answered my expe 
tion. During the cessation of respiration, | 
left ventricle ceased to beat, the right ventr 
retaining its function; on renewing its respi 
tion, nee ventricle resumed its beat. 
appears from this experiment, that from ¥ 
of a degree of irritabality equal to that of t 
right ventricle, and its own proper stimulus 
arterial blood, the left ventricle ceased its 
tractions. The function of the right ventri 
PSL) ’ 
DeCriory 
* Opera Omnia, Collegio Medicoram Londine 
edita, 1766, p. 28. -— 
+ Phil. Trans. vol. ii. : 
t On the Connexion of Life with Respira 
London, 1788, p. 72, 82 note, al 
