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Q.
Which one is absent in frog?
Jharkhand CECEJharkhand CECE 2006
Solution:
The 37 pairs of spinal nerves of rabbit are divisible according to the regions of backbone, into five gropus as, cervical (eight pairs), thoracic (twelve pairs), lumbar (seven pairs), sacral (four pairs) and caudal or coceygeal (six pairs). The ventral rami of first four pairs of cervical nerves anastomose to form a cervical plexus on each side. Three slender branches one each from the ventral rami of third fourth and fifth cervical nerves on each side constitute a phrenic nerves to innervate the diaphragm (diaphragm is absent in frog). In frog the renal portal first run forwards for some distance along the outer border of kidney of its side and then enters into it and breaks into capillaries. The venous blood is returned from each kidney by four to six short revenal veins, emerging out from its inner margin.