TYPES OF RESPIRATION. 389 



Sacro-lumbalis. This muscle is situated at the posterior 

 portion of the abdomen and thorax. Its fibres pass from its 

 origin at the sacrum, upwards and a little outwards, to be 

 inserted into the six inferior ribs at their angles. In expira- 

 tion it draws the ribs downwards, acting as an antagonist to 

 the lower levatores costarum. 



There are some other muscles which may be brought into 

 action in forced expiration, assisting in the depression of the 

 ribs ; such as the serratus posticus inferior, the superior fibres 

 of the serratus magnus, the inferior portion of the trapezius ; 

 but their function is unimportant. 1 



Types of Respiration. In the expansive movements of 

 the chest, though all the muscles which have been classed as 

 ordinary inspiratory muscles are brought into action to a 

 greater or less extent, the fact that certain sets may act in a 

 more marked manner than others has led physiologists to 

 recognize different types of respiration. Following Beau 

 and Maissiat, three types are generally given in works on 

 physiology : 2 



1. The Abdominal type. In this, the action of the dia- 

 phragm, and the consequent movements of the abdomen, are 

 most prominent. 



2. The Inferior Costal type. In this, the action of the 

 muscles which e~xpand the lower part of the thorax, from 

 the seventh rib inclusive, is most prominent. 



3. The Superior Costal type. In this, the action of the 

 muscles which dilate the thorax above the seventh rib, and 

 which elevate the entire chest, is most prominent. 



1 It is uncertain whether the straight muscles of the abdomen are ever con- 

 cerned in expiration. From their situation, it might be supposed that they would 

 have some action in the more violent phenomena of expiration, such as sneezing, 

 coughing, crying, etc. ; but Beau and Maissiat, who have investigated these ques- 

 tions very carefully, state that in dogs they have never seen these muscles act, 

 even in the most violent efforts. (Archives Generales, 4th series, vol. Hi.) 



3 Loc. cit. 



