A LESSON IN COMPARATIVE ZOOLOGY. 411 



a continuous column, or backbone, mark the distinctive features of the whole 

 order — viz , Vertebrates. 



From the upper part of this spinal column are given off twelve pairs of ribs, 

 which, nearly meeting in front, form a bony cage containing the heart and lungs. 

 The upper extremities are formed by a scapula and a clavicle, a humerus, 

 radius, ulna, carpus, metacarpus and phalanges. 



At the lower end of the spinal column is the pelvis, from which is given off 

 the femur, the tibia and fibula, the tarsus, metatarsus and phalanges to form the 

 lower extremities. 



This briefly is man. 



In the Simidse, or monkeys, the facial angle is a little greater, the humerus, 

 the radius and ulna a little longer, the tarsus slightly modified, and in some spe- 

 cies the vertebrge are extended into a tail. These are monkeys, modified a little 

 from man. 



In the Felidse and the Canidae, the facial angle is still greater, the teeth sharp 

 and cutting, with well developed canines, the upright position is changed to a hori- 

 zontal posture, the upper extremities are now fore limbs, bones modified in shape, 

 species mostly digitigrade. The bears all plantigrade. 

 General plan same as man. 



In the remaining members of the Carnivorse, as the sea lion, seal and wal- 

 rus, the fore limbs are modified into paddles, while the hind limbs are less de- 

 veloped. In the walrus the lower incisors and canines are absent, while the up- 

 per incisors are elongated into tusks. 

 General plan same as man. 



In the Bovidse, beginning with the camels and running through the llama, 

 giraffe, ox, bison, yak, goat, zebu, gazelle, gemsbok, sheep, antelope and deer, 

 we have an elongated skull, modified bones of the fore and hind limbs, and a 

 modification also of the carpus and metacarpus, the tarsus and metatarsus, where- 

 by the foot is cloven, owing to consolidation of some of these bones. In some of 

 the members of this order we have the horn, either deciduous or permanent, and 

 in all the cauda. In some, also, we have a longer scapular and longer spinous 

 processes. This affords greater attachments to the nuchal ligaments and muscles 

 for those animals with heavy heads and horns. In the giraffe this is especially 

 noticeable. The shoulders are so high that it makes the fore legs seem 

 higher than the hind legs. This is due to the lengthened scapula and spinous 

 processes. The heads of the femur and humerus are on the same leve. 

 In all other respects, the general plan is the same as man. 

 In the Cetacea, as the porpoise, dolphin and whale, the skeleton is the same, 

 except the hind limbs are modified into complete or rudimentary fins. 



In the extensive orders of Insectivora, Rodentia, Edentata and Marsupiala, 

 the general plan is that of the higher animals and of man, modified to meet the 

 requirements of its mode of life. 



In the enormous class of Aves, or birds, beginning with the robin and end- 

 ing with the penguin, we have the elongated skull ending in a beak or bill, light 



