The Limbs 



343 



Fig. 6i. Peromelus Apus. (Gurlt) 



FiCr. 62. Pbromelus Achirus, Foal. 



later arise the vertebral column, the skeletal lauiscles, tendous 

 and ligaments and the corium, or deeper layer of the skin. 



The formation of the limbs begins as small buds, or outgrowths, 

 arising from the mesoblastic somites soon after the third week in 

 the human embryo, earlier in the rabbit and probably in most of 

 our domestic mammals. The limb-buds each represent several 

 mesoblastic somites, as indicated by the fact that the nerves pass- 

 ing to each limb are formed by the union of branches from sev- 



