20 THE DESCRIPTIVE ANATOMY OF THE DOG. 



purifying the whole by processes which are now becoming daily 

 more and more intelligible. 



THE SKELETON consists of the skull, trunk, and extremities. 

 The skull is hollowed out to contain the brain, and also the eye, 

 ear, nose, and tongue ; it is attached to the trunk by the neck, 

 which is the commencement of a series of hollow bones united 

 together to form a canal extending from the head to the tail, 

 and containing a continuation of the brain in the form of a 

 compound nerve the spinal marrow, as it is commonly called. 

 The trunk is formed of this chain of bones called the spine 

 (divided into the seven cervical, a b, thirteen dorsal, b c, and 

 seven lumbar vertebrae, c d), and, extending backwards still 

 further, of the sacrum or rump-bone d e, attached to which are 

 the twenty bones of the tail e /, which are no longer hollow 

 for the lodgment of the spinal marrow. Besides the spine, the 

 trunk is composed of the thirteen ribs b c h, attached to the 

 thirteen dorsal vertebras b>y ligamentous bands, and forming, with 

 the breast-bone (Fig. 2, q\ the thorax or chest, for the protec- 

 tion of those important parts, the lungs and heart, and partially 

 also the stomach and liver. To the sacrum, also, are attached by 

 similar ligaments the hip-bones g Ji 9 for the purpose of affording 

 protection to the bladder, and to the uterus, &c., in the female, 

 and to give a firm fulcrum to the hind- legs, which are the main 

 organs of propulsion. In the dog, as in the horse, there is no 

 collar-bone, and the only attachment between the fore-legs and 

 the body is muscular, so that the chest is as it were slung 

 between the shoulder-blades on the fore-legs. By this arrange- 



