121 



Third. — At the digastrics, for the union between 

 the central and neck S, covering, to some extent, 

 also the third S. 



Fourth. — At the head joint, for the formation of 

 the bi-composite spine, covering the whole. 



•The second and third are those by which the 

 two ends of the composite S are formed. 



The fourth and first unite in their action after 

 the action of the third and second, so that the 

 central focus is always between the lung lobes. 



The action of the digastrics, in representing the 

 central uniting with the neck S through the neck- 

 root joint, is similar to that of the diaphragm in 

 uniting the central and the third S, the flat an- 

 terior part of the diaphragm (§ 106) being the ana- 

 logue of the anterior portion of the digastrics, the 

 diaphragm pillars of the posterior portions. The 

 psoae complete the action, and join it with the in- 

 ternal obliques of the eyes. 



The various S S of the snake are discharged in 

 succession ; those of the higher animals are col- 

 lected together under one S — the ." bicomposite " — 

 by means of the neck and then discharged together. 



§ 119. The above is the gathering movement, 

 and determines the action of the legs of appui. 

 The free legs are moved in the discharge. In 



