VERTEBUATES. 



135 



veins, a system of capillary vessels, which are minute tubes 

 connecting the ends of the smaller arteries with the smaller 

 veins. There are no genuine capillaries in the lower ani- 

 mals exactly comparable with those of vertebrates. 



The blood is red in all the vertebrates except the lance- 

 let, and besides white corpuscles contains red corpuscles. 

 While fishes and tadpoles breathe by gills, all land and am- 

 phibious vertebrates breathe the air directly by lungs con- 

 nected by a windpipe {trachea) with the mouth. The 

 nervous system consists of a brain and spinal cord. The 

 brain consists of four pair^ of lobes, i.e., the olfactory 



Fig, 176.— a diagrammatic section across the body in the chest region, x, the 

 dorsal tube, which contains the spinal cord ; the blaclt mass surronndn]C it is 

 a vertebra; a, the gullet, a part of the alimentary canal; h, the heart; sy, 

 sympathetic nervous system; 1 1, lungs; the dotted lines around them are the 

 pleurae; rr, ribs; s(, the breastbone. From Martin. 



lobes, cerebral hemisjiheres, the optic thalami with the 

 pineal gland, and the optic lobes; besides these lobes, which 

 are arranged in pairs, there are two single parts of the 

 brain, the cerebellum and the beginning of the spinal cord, 

 called the medulla oMoiu/ata. 



The limbs each consist of a single long bone, succeeded 

 by two long bones, followed by two transverse rows of 

 short wrist or ankle bones, and five series of long finger or 

 toe bones called phalanges. For example, in the fore limb 

 of most vertebrates, as in the arm of man, to the shoulder 

 girdle is articulated the humerus; this is succeeded by the 

 ulna and radius; these by the wrist-bones or carpals, and 



