SPINAL NERVES 



353 



At the points where the anterior and lateral terminal rami arise, connecting 

 loops may extend from one spinal nerve to another. Thus in the cervical region 

 superficial and deep nerve plexuses are formed. The deep cervical plexus forms 

 the ansa hypoglossi and the phrenic nerve. 



Veslcula audit! va 



Gang, acusticum 



Gang, semilunare n.V 

 Cerebellum 



Gang, radii-is n.IX 

 Gang, petrosuni 



Gang, radlcis n.X 



N. frontalis- 



,Gang. Frorlep 

 N. hypoglossus 



I.C 



-N.XI. 



Gang, nodes. 



---N. desc. cerv. 



---Rami hyold. 



(Ansa hypoglossl) 



.-.N. Musculocutan. 

 N. axillarls 

 N. phrenicus 



"N. medianus 



N. radtalis 



N. ulnarls 



-ITh. 



I Co 



N. tibialis 

 N. peroneus 



Tubus digest. ^ 



N. femoral 

 N. obturator 



R. posterior 



R. terminalis lateralis 

 R. terminalis anterior 

 Mesonephros 

 Nn. ilioing. et hypogastr. 



FIG. 341. Reconstruction of the nervous system of a 10 mm. embryo (Streeter). X 12. 



The Brachial and Lumbo-sacral Plexuses. The nerves supplying the arm 

 and leg also unite to form plexuses. In embryos of 10 mm. (Fig. 341) the trunks 

 of the last four cervical nerves and of the first thoracic are united to form a flat- 

 tened plate, the anlage of the brachial plexus. From this plate nervous cords 



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