30 



Anatomy of the Rabbit. 



THE SKELETAL SYSTEM*. 



' That portion of the skeleton which in the adult is designated as axial 

 includes the vertebral column, together with the associated ribs and 

 sternum, and the skeleton of the head. The axial relation belongs in the 

 first instance to the bodies of the vertebrae and to a small portion of the 

 base|of the skull. A line drawn through the centres of the vertebral 

 bodies indicates the position of the primary axial support, the notochord. 



.ius. 



ao..... 



Fig. 21. Schematic representation of the chief organ-systems of a generalized 

 vertebrate as seen in a transverse section of the abdominal region: 



Integument — int. 



Skeleton — v., vertebral body; a. v., vertebral arch; c. v., vertebral canal. 



Muscular system — s.m., skeletal muscle;' v.m., visceral muscle., v . . . . . 



Nervous system — m.s., spinal cord, with the central canal, and the dorsal (pos- 

 terior) and ventral (anterior) roots of the spinal nerves; g.r.p., ganglion of the 

 posterior root; r.c, ramus communicans to sympathetic trunk; r.m.a. and 

 r.m.p.. anterior and posterior rami of a spinal nerve; t.s., sympathetic trunk. 



Digestive system — i., intestine. 



Vascular system — ao., aorta. 



Urinogenital system — k., kidney; go., gonad (ovary or testis). 



Serous cavity — c.p., general coelom, pleuroperitoneal, or peritoneal cavity; 

 p. v. and p.p., visceral and parietal parts of the serous tunic— visceral and parietal 

 peritoneum; mes., mesentery. 



The arches of the vertebrae are identified with the general functions of 

 support of the related musculature and enclosure of the spinal cord. In 

 lower vertebrates the line formed by the vertebral column and the base 

 of the skull is for the most part straight. In a mammal the vertebral 



*The majority of the features mentioned below are illustrated in the plate 

 figures of regional sections of the rabbit-foetus which follow, and for this reason the 

 references are not indicated except in special cases. 



