252 Descriptive Zoology. 



The Excretory Organs of the Rabbit. The lungs act as 

 excretory organs, throwing off carbon dioxid as well as ab- 

 sorbing oxygen. The kidneys also are organs of excretion. 

 The kidneys are bean-shaped bodies attached to the dorsal 

 wall of the abdominal cavity. To each kidney runs a branch 

 of the aorta, supplying it with blood, and from the kidney a 

 vein returns the blood to the postcaval vein. As the blood 

 flows through the kidney in fine tubes called capillaries, the 

 kidney removes from it certain impurities, especially the 

 waste matter that contains nitrogen. The excretion is con- 

 veyed backward by a tube called the ureter, and emptied 

 into the urinary bladder, an organ not possessed by the 

 birds or reptiles. 



Enemies of the Rabbit Among the enemies of the rab- 

 bit are dogs, wolves, foxes, cats, both wild and domesticated, 

 minks, weasels, hawks, owls, and perhaps many others. In 

 addition to these larger foes, the rabbit is usually infested 

 by parasites, such as fleas, tapeworms, etc. 



How the Rabbit escapes his Enemies. The rabbit has 

 claws, but they are not very efficient as a means of defense. 

 Rabbits use their teeth in fighting one another, but these 

 avail nothing against their enemies. The rabbit is practi- 

 cally defenseless, and relies upon two means for protec- 

 tion, the first is its color, and the second its speed of flight. 

 The prevailing color of the rabbit is gray, varied with some 

 blackish, and more or less tinged with yellowish brown. In 

 the summer he appears rather more rusty or tawny. He is 

 so like his surroundings that it takes a keen and practiced 

 eye to detect him when he sits perfectly quiet in his form. 

 This he usually does, relying on his color to protect him. 

 Besides his color, his position is an aid in concealment, for 

 he is snugly doubled up, the ears folded down closely along 

 the back, and the white tail is out of sight. He generally 



