DOMESTICATED ANIMALS 47 



neys and two lungs. But in birds, for some rea- 

 son, the right ovaiy does nothing, and has shriv- 

 eled to a mere remnant. 



In man and most other vertebrate animals there 

 are two bones in the leg from the knee to the ankle 

 — the tibia and the fibula. In birds and in some 

 manmials there is but one bone (tibia), the fibula 

 being represented by a mere splint extending 

 down pai-t way from the knee. You have prob- 

 ably seen this splint without recognizing it in the 

 leg of the chicken. The big bone in the chicken's 

 leg is the tibia ; the splint is the vestigial fibula. 



Insects ordinarily have two pairs of wings. But 

 flies have only one pair, the hind pair being repre- 

 sented by a couple of knobs. In other species of 

 insects the front wings are rudimentary. The 

 male cockroach has two pairs of wings, and occa- 

 sionally uses them in flying. But the female is 

 flightless, the wings being rudimentary. The ovar- 

 ies are vestigial in the working class of bees and 

 ants. In the cow there are two teats that are rudi- 

 mentary and four that produce milk. The rudi- 

 mentary teats occasionally }deld milk. In one 

 breed of Chinese sheep the ears are mere vestiges, 

 and in another breed the tail has dwindled to **a 

 little button smothered in fat.'' In tailless dogs 

 and cats there is a rudimentary stump. In some 

 breeds of chickens the comb and wattles are rudi- 

 mentary; and in the Cochin-China the spur has 

 nearly disappeared. In the hornless breeds of 

 sheep and cattle tiny knobs often grow out where 



