RESPIRATION 355 



room is provided for the abdominal viscera, the strain is taken 

 off the muscular abdominal wall. As a result, although the 

 actions of the diaphragm are not suspended, they are not 

 indicated by the outward bulging of the abdominal wall, which 

 is no longer necessary. Expiration is caused by the elastic 

 recoil of the ligaments of the costo-vertebral and the chondro- 

 sternal joints. The accompanying diminution of the infra- 

 costal angle acts through the abdominal viscera to restore the 

 diaphragm to its position of rest. 



The Cheyne-Stokes type of respiration is exhibited in the 

 late stages of arterio-sclerosis, uraemia and other conditions. 

 Pauses, during which respiration is completely inhibited, 

 alternate with phases in which the respiratory excursions 

 gradually increase to a maximum and then gradually diminish. 

 Traube has suggested that, owing to the disease, the excit- 

 ability of the respiratory centre is decreased. During the 

 pause the blood becomes increasingly venous in character 

 and eventually the centre responds to a stimulus which is 

 abnormally strong. The oxidation of the blood by the 

 respiratory phase weakens the stimulus so that it again becomes 

 insufficient to bring about a response. 



The phenomenon known as hiccough is due to a spasmodic 

 contraction of the diaphragm, accompanied by a spasmodic 

 closure of the glottis. It is usually a reflex result of stimula- 

 tion of the stomach, heart, peritoneum, etc. 



Paralysis of the Diaphragm. When the diaphragm is 

 paralysed, the intercostal muscles are required to produce 

 a still greater increase in the transverse and antero-posterior 

 diameters of the thorax, and in this they are aided by all the 

 extraordinary muscles of respiration. The consequent increase 

 in the capacity of the abdomen, which is due to the widening 

 of the infra-costal angle, causes the anterior abdominal wall to 

 collapse in the epigastric region with each inspiration. 



Respiration in Emphysema. In emphysema the capacity 

 of the thorax in the position of rest is increased to its maximum, 

 so that the intercostal muscles are thrown out 'of action. The 



