428 THE ANATOMY OF VEETEBEATED ANIMALS. 



versing the diaphragm, the vena cava is surrounded, for 

 about an inch, by a layer of red circtdar muscular fibres. 

 The aorta and the pulmonary artery are both dilated at 

 their commencements. 



The penis of the male is contained within a prepiice, 

 supported by a loop of the cutaneous muscle. There is a 

 large os penis, which presents a groove for the urethra 

 inferiorly. The prostate is small, and there are no vesiculse 

 or Cowper's glands. The testes lie just outside the inguinal 

 canal. The anus and the vulva of the female are surrounded 

 by a common fold of integument. The clitoris has no 

 bone. The body of the uterus is divided by a longitvidinal 

 septum. 



II. The Proboscidea. — These are massive animals, walking 

 upon the extremities of the five toes, with which each font 

 is provided, and upon a great tegumentary cushion which 

 unites these, and forms a flat sole behind them. 



The nose is prolonged into a flexible proboscis, which is 

 at once a strong, and a delicate, organ of prehension. The 

 hairy covering is scanty in the recent species; but there 

 was abiindant long hair, and an undercoat of wool, in at 

 least one extinct Proboscidean, the Mammoth {Elephas pri- 

 migenius), which ranged over Northern Europe and Asia 

 dui-ing the glacial epoch. The pinna of the ear is large 

 and flat. The testes of the male remain in the abdomen, and 

 the mammee of the female are placed between the fore 

 limbs. 



The dorso-lumbar vertebrae amount to as many as twenty- 

 three, and not more than three of these are lumbar, so that 

 the dorsal region is, proportionally, exceedingly long. There 

 are four sacral vertebrae, followed by a comparatively short 

 tail. The centra of the vertebrae are far more flattened, 

 from before backwards, than those of any other teri-estrial 

 mammal, and this is particularly the case in the cervical 

 region, whence it follows that the neck is extremely short. 



The skidl is enormous, even in proportion to the body, 

 its size arising, in great measure, from the development of 

 air cavities in the diploe. The interspace between the 



