1895.] 



ANATOirr OF PIPA AMEBIC AXA. 



831 



muscle arises from the thigh close to the rectus femoris '. This 

 runs forward, increasing in breadth and undergoing a corresponding 

 diminution in thickness ; ultimately it fans out over the back of 

 the lung and of the oesophagus ; it begins to be attached to the lung 

 tirsfc at the origin of the smaller lobe of that viscus. I cannot but 

 think that the close attachment of the muscle to the lung must 

 have some relation to the function of respiration. 



The main mass of the muscles, however, go past the lung, and are, 

 as already stated, inserted upon the oesophagus. At their insertion, 

 which is on the median ventral side, they not only fan out, but the 

 muscle becomes separated into a number of small separate bundles. 

 The corresponding muscle of the opposite side of the body has to 

 perforate the mesentery on its way to be inserted on to the oeso- 

 phagus. All the fibres of the muscle are not, however, inserted in 

 this way on to the oesophagus ; a good number of them fan out 



Fig. 2. 



st.h. 



Pipa surinaraensis. 



Dissection to display diaphragm. 



o.d., oviduct ; a, branch of obliquus muscle ; st.h,, sternohyoid. 

 Other letters as in fig. 1. 



dorsally and are inserted on to the aponeurosis already spoken of, 

 which shuts off the abdominal cavity in front. The arrangement 

 of these fibres is shown in the accompanying drawing (fig. 2). 



' See p. 839. 



53* 



