416 REPORT—1840. 
probably thus drawn down by the re-expansion of the cartilagi- 
nous rings of the tubes, now set free by the relaxation of their 
contractile fibres. On cutting into the lung the trachea and 
bronchi were found unusually open, and filled with tenacious 
froth. In another instance in which this experiment was re- 
peated, the rise after the injection of diluted ammonia amounted 
to 12 inch. 
13. The experiment was repeated with saturated solution of 
common salt, with similar results. 
14. The following experiment illustrates several of the same 
points; and further shows the character of the sensibility in 
different parts of the air-passages. Subject, a large Newfound- 
land dog. The trachea was exposed and divided below the cri- 
coid cartilage. It was then held out by a hook. On being ir- 
ritated by a scalpel, the membranous portion gradually con- 
tracted until the ends of the cartilaginous rings met. The 
contraction was somewhat increased by galvanism. The appli- 
cation of salt caused no further effect. None of these irritations 
excited cough or sign of uneasiness ;_ but on passing the finger 
upwards to the larynx, violent expiratory efforts were excited, 
and the glottis very forcibly closed on the finger. The expira- 
tory efforts forced a little bloody mucus from the trachea. A 
scalpel was introduced into the trachea as far as its bifurcation, 
and scraped against the membrane. No cough followed for some 
time ; but on repeating the experiment about a minute after, 
cough ensued, and increased on subsequent trials. The salt ap- 
plied caused a secretion of bloody mucus. The blood-vessels 
in the upper part of the chest were now cut into, when the rare 
deep inspirations preceding death by hemorrhage succeeded. 
The heart continued to beat several seconds after the cessation 
of respiration. The bronchi exhibited full indications of con- 
tractility on the application of galvanism, or of salt, or ammo- 
nia. The upper part of the trachea, which had during life been 
irritated with salt and galvanism, was now found quite expanded, 
the portions lower down were half-expanded. Both contracted 
slightly on being galvanised, and completely on dividing their 
cartilaginous rings. 
Having satisfactorily proved the existence of irritable con- 
tractility in the air-tubes, I next proceeded to try how this would 
be influenced by various medicinal agents which we are in the 
habit of using in various diseases of the organs of respiration. 
15. A rabbit was poisoned by dropping some strong hydro- 
cyanic acid intoitsmouth. In thirty seconds it was seized with 
convulsive and gasping breathing, and opisthotonic spasms, and 
died in ten seconds more. Galvanism produced no results with 
