108 PHILOSOPHICAL TRANSACTIONS. [aNNO I667. 



knife, passing the knife but just into the cavity of the breast (which you may 

 know by finding no resistance to the point of it ;) then take it out, and put in 

 a director or a small quill made like it, and thrust it in about an inch, directing 

 the end of it toward the sternum close to the inside of the breast. Then cut 

 upon it about an inch on the intercostal muscles ; by which you may be secured 

 from touching the lungs with the poitit or edge of your knife. This done, put 

 in your finger, and with your nail separate the nerve which passes along the 

 side of the pericardium toward the diaphragm. Then put in a probe, a little 

 inverted at the end like a hook, and lay hold of the nerve and pull it to the 

 orifice of the breast, and cut it oW, and sew the hole vip very close. Do the 

 same on the other side, and presently let the dog loose, and you will plainly 

 see him draw his breath exactly like a wind-broken horse. Which yet you will 

 see plainer if you run him a little in a string after he is cut. But that any one 

 may perform this experiment the easier, let him first take notice how the nerves 

 of the diaphragm pass along on each side of the pericardium in a dead animal, 

 before the trial be attempted in a living one. 



The most obvious remarks upon this experiment are : 



1. That the whole manner of respiration is quite altered. For, as in a sound 

 Animal, in inspiration the belly swells by the lifting up the bowels by the con- 

 traction of the diaphragm ; and in exspiration the belly falls by the relaxing of 

 the same : in a wind-broken dog or horse it is quite contrary ; for in them it 

 is to be seen plainly, that when they draw their breath, their belly is drawn 

 in very lank and small, and when they breathe up, their belly is relaxed and 

 swells again. 



2. It being certain that the lungs do not move of themselves at all, but 

 wholly depend upon the expansion of the thorax by the intercostal muscles and 

 the diaphragm ; by this experiment it appears how much the single motion of 

 either of them particularly contributes to respiration. For all inspiration being 

 made by the dilatation of the thorax, and that dilatation being caused partly by 

 the intercostal muscles drawing up the ribs, and partly at the same time the 

 diaphragm by its contraction drawing downward the lower small ribs, to which 

 it is joined, and also lifting up the viscera of the lowxr belly, by which they 

 jointly make all the space they can, for the air to come in and distend the 

 lungs : it must hence necessarily follow, that the intercostal muscles and the 

 diaphragm being constituted for two distinct employments (though both to the 

 same end) and neither being able to perform the other's office, where one 

 ceases from its work, the other for the exigence of nature must take more 

 pains to supply the defect of the former. Which is very evident to be seen; for 

 the diaphragm being made useless by losing its nerves, the intercostal muscles 



