172 



THE VITAL FUNCTIONS. 



and ninscular apparatus which surrounds it, seen from the 

 lower side. In the hist of these figures, a is the tapering 



336 



^ )i if 



f 



prolongation of the tube, proceeding towards the head of tlie 

 insect; v, one of the dilated portions, or ventricles, as they 

 have been called, of the dorsal part of the tube; f, one of the 

 small tendinous folds, to which the ligamentary bands are 

 attached; and l is one of these bands, having a triangular, 

 or, if considered as continuous with that on the other side of 

 the vessel, a rliomboidal shape, and attached at h, to the su- 

 jierior segments of the abdomen. At i is seen a layer of the 

 same fibres, wliich are partly ligamentous and partly muscu- 

 lar, passihg underneath the dorsal vessel, and forming, in 

 conjunction with the layer that passes above it, a sheath, 

 which embraces and fixes that vessel in its place: these in- 

 ferior layers have been removed from the other parts of the 

 vessel, to allow the upper layers to be seen, as is the case at 



