540 
MR. SIBSON ON THE MECHANISM OF RESPIRATION. 
air in the lungs. By no muscular effort can a child that has once breathed force out 
the whole of the air from its lungs. If we compress the chest after death, a portion 
of air is pressed out through the trachea ; on removing the pressure the resiliency of 
the walls of the chest draws as much air into the lungs as was previously expressed; 
an incomplete but artificial inspiration can thus be performed. A very simple appa- 
ratus, acting on this principle, is recommended in the Humane Society’s Report for 
1834, p. 126. The chest is compressed by a many-tailed bandage, the tails of which 
cross each other ; when they are alternately tightened and relaxed they excite arti- 
ficial respiration. A syringe has been constructed to act on the same principle ; after 
it draws a portion of air out of the lungs through the trachea, fresh air, being ad- 
mitted, rushes in to supply its place ; in both these cases the lungs are expanded by 
the elasticity of the parietes of the chest. 
I conceive that respiration after the first breath is essentially performed by mus- 
cular actions ; at the end of each expiration the elasticity of the walls of the chest 
will tend to commence the next inspiration; until the walls of the chest arrive at 
the medium size, or that which they retain after death, the elasticity will act along 
with the muscles ; as soon as they have passed beyond this point, the elasticity will 
tend to act against the muscular actions ; indeed these have to overcome the elas- 
ticity. At the end of an inspiration, elasticity will commence the expiration, assist 
in the action up to the neutral point, and resist it beyond that point. Thus elasticity 
as an agent in respiration balances itself. 
I would not have remarked on the elasticity of the walls of the chest as a respira- 
tory agent, but for a short note from Mr. Hutchinson, informing me that he was 
inquiring into the subject. From the success of his previous inquiries I look forward 
to his communication with much interest. 
99. The child *. 
In the child, the liver and the stomach, and other abdominal viscera push the 
diaphragmatic set of ribs and the cartilages of the intermediate set forwards and out- 
wards, and cause them to project beyond the thoracic set of ribs, as the girt of the 
abdominal organs is considerably greater than that of the thoracic. When the dia- 
phragm descends, the lungs and heart occupy the place previously taken up by abdo- 
minal viscera, and as the lungs are smaller than the viscera they replace, the lower 
end of the sternum and xyphoid cartilage, the conjoint cartilages of the sixth and 
seventh ribs, and the sixth rib fall backwards on inspiration owing to the pressure 
of the atmosphere. If the inspiration be so deep as to bring the lungs down to the 
lower edge of the floating cartilages, all those cartilages fall backwards also, and 
those of the opposite side approach each other. 
As the proportion of the abdominal to the thoracic viscera lessens as life advances, 
the lower cartilages gradually cease to fall backwards during inspiration, and after- 
* Figs. XXI. a. b., XXII. a. b. Archives of the Royal Society. 
