SPINAL NERVES 



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between the second and 

 third vertebrje, and each 

 is soon joined by the small 

 third nerve {III) which 

 emerges between the third 

 and fourth vertebrae, as well 

 as by a small branch or two 

 from the first, thus forming 

 a simple network ox plexus 

 — the brachial plexus (br. 

 pi), from which pass off 

 nerves to the fore-limb, 

 supplying both skin and 

 muscles. 



The fourth, fifth, and 

 sixth nerves take a very 

 similar course. The fourth 

 {IV) emerges between the 

 fourth and fifth vertebra, 

 the fifth {V) between the 

 fifth and sixth, and the 

 sixth ( VI) between the sixth 

 and seventh. They all pass 

 obliquely backwards, and 

 supply the walls of the 

 body, being distributed to 

 both skin and muscles. 



The seventh, eighth, and 

 ninth nerves supply the 

 muscles and skin of the 

 hind limbs. The seventh 

 {VII) leaves the neural 

 canal between the seventh 



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PRACT. ZOOL. 



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Fig. 51. — The ventral branches of the 

 spinal nerves and the sympathetic of 

 the frog, from below : shown on the 

 right side only. 

 / — X^ spinal nerves ; Ao. systemic arch ; 

 br. pi. brachial plexus ; C. calcareous 

 bodies which surround the spinal 

 ganglia ; D. Ao. dorsal aorta ; fern. 

 femoral nerve ;■//. A. iliac artery ; sci. 

 sciatic nerve ; sci. pi. sciatic ple.xus ; 

 Sk. skull ; Sp. A . splanchnic artery ; 

 .Sy. sympathetic cord ; Sy. c. commun.- 

 eating branches between the sympa- 

 thetic and spinal nerves ; Sy. g. 

 sympathetic ganglia ; Ust. urostyle ; 

 V- — y^. centra of vertebrse ; V^g. vagus 

 nerve, with its ganglion. (After 

 Gaupp. slightly modified.) 



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