654 EXTERNAL ANATOMY OF INSECTS. 
of losing them, renders it difficult to ascertain what is 
the natural number of pairs in any species. 
2. Kinds. Upon a former occasion I gave you a suf- 
ficiently full account of the kinds.of legs*, and I have 
also assigned my reasons for giving a different denomi- 
nation to the anterior legs under certain circumstances?; 
I shall not therefore enlarge further upon this head. 
8. Substance. The substance of the legs is generally 
regulated more or less by that of the rest of the body, 
only in soft-bodied insects they seem usually more firm 
and unbending. Each joint is a tube, including the 
moving muscles, nerves, and air vessels. 
4. Articulation with the Trunk. M. Cuvier has ob- 
served that the hip (cora), which is the joint that unites 
the leg with the body, rather inosculates, in its acetabu- 
lum, than articulates in any precise manner‘; but this 
observation though true of a great many, will not apply 
universally, for the legs of Orthopterous imsects, and of 
most of the subsequent Orders, are suspended rather than 
inosculating. Even in many Coleoptera a difierence is 
observable in this respect. I have before mentioned that 
what are called the puncta ordinaria, which distinguish 
the sides of the prothorax of many Scarabeide and Geo- 
trupide, form a base for an elevation of the interior sur- 
face with which the extremity of the base of the clavicle, 
which plunges deep into the breast, ginglymates*; this 
structure may also be found in other Lamellicorns, as 
the stag-beetle (Zucanus) and Dynastes, that have not 
those excavations; in these last it is an elevated ridge 
forming a segment of a circle with, it should seem, a 
* Vor. If. p. 302—. 359—. 361. » See above, p. 544—. 
© Anatom. Compar. i, 453. ‘ See above, p. 398. 
