240 ANATOMY. 



cess, which Kirby and Spence cull the postfurca, Audouin, on the con- 

 trary, styles it, in connection with the preceding ones of the pro- and 

 mesothorax, the entothorax *, we rind but a few other ridges produced 

 by the sutural connection of the pleurse with the sternum ; these are 

 Audouin's apodemata, which vary in their course according to the 

 varying forms of the parts, and are of much less importance. 



166. 



INTERNAL SKELETON OF THE ABDOMEN. 



The abdomen has no internal skeleton, but consists of horny rings 

 connected together by a flexible membrane, and each of which is divided 

 into a dorsal and a ventral plate. In the grasshoppers, at least Gryllus 

 and Locusta, horny half circles arise from the lateral edges of each 

 dorsal plate, which are about one-third of its width, and extend as 

 high as the dorsal depression. It is to these arches that the long air 

 bags are attached, which form a zigzag, and which we have fully 

 described above. Marcel de Serres f, who first discovered and de- 

 scribed them, called them ribs, a comparison which in so far is not 

 inappropriate, from their encompassing and protecting the air bags of 

 these creatures. But they are properly elastic processes, which are in 

 a directly opposite action to that of the oval air bags, which they dis- 

 tend by springing back, when the contraction of the spiral fibre has 

 shortened them, and has thereby removed the process to which the bag 

 is attached from the abdominal plate. They consequently belong to 

 the respifatory system, and were considered under it by their first 

 discoverer. 



167 



SKELETON OF THE LIMBS MODE OF ARTICULATION. 



The skeleton of the limbs is merely external, and as such it has been 

 sufficiently described above ( 79) in a preceding division ; we have 

 also there indicated the way in which the different parts of a limb are 

 connected together, it therefore remains merely necessary here to give 

 a special description of all the different kinds of articulation both of 

 the limbs as well as the other portions of the skeleton. 



I. CONNECTION WITHOUT MOTION (si/narthrosis}. This kind of 



* See Meckel's Deutsche Archiv., &r. torn. vii. p. 440. 

 [ f Mem.de Musee, torn. iv. (1819). 



