SKELETON 4 I 



the true nipple, in the other — the teat — the region around the open- 

 ings of the ducts becomes drawn out into a tube with the ducts 

 opening at the bottom (ungulates). 



THE SKELETON 



The term skeleton as used here is applied to any of the harder 

 parts of the body, developed from the mesoderm and serving for 

 support, for the attachment of muscles, for protection and the like. 



Fig. 33. — Diagram of the skeletogenous tissue in the caudal region of a vertebrate. 

 ov, blood-vessels; d, corium; epmu, epaxial muscles; hs, horizontal partition; hymy, 

 hypaxial muscles; msd, msv, dorsal and ventral median septa; mys, myosepta; w, spinal 

 cord; nc, notochord. 



This excludes any purely epidermal hard parts, and these have 

 been included with the integument. 



As the skeleton can only develop where there is mesenchyme; 

 the distribution of the chief skeletogenous parts, sometimes called 

 the membranous^eleton, may be given here, continuing the account 

 from page 21/ First is the corium, immediately beneath the epi- 

 dermis, forming an envelope around the internal structures. This 

 connects in the middle line, above and below, with a longitudinal 

 partition {msd and v) which separates the muscle masses of the 

 two sides. This partition splits to pass on either side of the central 



