196 Mayow 



but is carried downwards and outwards as it flattens. 

 So that the viscera of the abdomen, which were 

 previously contained in its concavity, are, now that it 

 has contracted, forced both downwards and outwards, 

 and the space in the thorax which was previously 

 occupied by the diaphragm and the said viscera is now 

 left free for the expansion of the lungs. And indeed 

 any one can feel in himself that the ribs rise in 

 inspiration, while the viscera of the abdomen move 

 both downwards and outwards under the pressure of 

 the diaphragm. But all this will be more evident 

 from an autopsy, for if the chest of any animal is 

 opened and the diaphragm pressed downwards by the 

 hand while the ribs are pulled upwards (and this is 

 not done without much pxertion), you will see that the 

 chest dilates and that its capacity is enlarged. But as 

 soon as the supporting force is withdrawn, the chest 

 will of itself contract anew. For the diaphragm, 

 pushed by the viscera in the lower part of the 

 belly, will soon rise into the cavity of the chest, and 

 the ribs, by descending forcibly to their natural posi- 

 tion, will still further diminish the cavity of the 

 thorax. 



Hence if the stomach be too full, or if the liver or 

 the rest of the viscera are much enlarged, respiration 

 cannot go on except with difficulty, inasmuch as the 

 said viscera, from their mass, press so much on the 

 diaphragm as to prevent it from descending and 

 enlarging the cavity of the chest. Still if, owing to 

 an urgent necessity for more vigorous breathing, the 

 violent contraction of the diaphragm forces the 

 abdominal viscera downwards, notwithstanding their 

 resistance, it not infrequently happens that its fibres 

 contract too much in consequence of the violent 

 strain, so that their tone is almost destroyed and 



