2QO DIGESTION. 



analogy of the case of the stomach with that of the other 

 hollow viscera, as the rectum, and bladder, may be also 

 cited in confirmation. 



Besides the influence which it may thus have by its con- 

 traction, the stomach also essentially contributes to the act 

 of vomiting, by the contraction of its pyloric orifice at the 

 same time that the oblique fibres around the cardiac orifice 

 are relaxed. For, until the relaxation of these fibres, no 

 vomiting can ensue ; when contracted, they can as well 

 resist all the force of the contracting abdominal and other 

 muscles, as the muscles by which the glottis is closed can 

 resist the same force in the act of straining. Doubtless 

 we may refer many of the acts of retching and ineffectual 

 attempts to vomit, to the want of concord between the 

 relaxation of these muscles and the contraction of the 

 others. 



The muscles with which the stomach co-operates in con- 

 traction during vomiting, are chiefly and primarily those 

 of the abdomen ; the diaphragm also acts, but not as the 

 muscles of the abdominal walls do. They contract and 

 compress the stomach more and more towards the back 

 and upper parts of the diaphragm ; and the diaphragm 

 (which is usually drawn down in the deep inspiration that 

 precedes each act of vomiting) holds itself fixed in contrac- 

 tion, and presents an unyielding surface against which the 

 stomach may be pressed. It is enabled to act thus, and 

 probably only thus, because the inspiration which precedes 

 the act of vomiting is terminated by the closure of the glottis ; 

 after which the diaphragm can neither descend further, 

 except by expanding the air in the lungs, nor, except by 

 compressing the air, ascend again until, the act of vomiting 

 having ceased, the glottis is opened again (see diagram, 

 p. 231; see also p. 233). 



Some persons possess the power of vomiting at will, 

 without applying any undue irritation to the stomach, but 

 simply by a voluntary effort. It seems also, that this 

 power may be acquired by those who do not naturally 



