MAMMALIA, 529 



The ribs in the cat and dog form a compact thorax 

 which, however, is remarkably narrow from side to side. 

 The explanation of this peculiarity will be found in Chapter 

 XXVI. (Sternum and Ribs). 



The limbs are fairly long and about equally developed. 

 They resemble each other (dog and cat) far more closely 

 than do those of the horse and ox. Both types are digiti- 

 grade and unguiculate (little claws or unguiculae on each 

 toe). There are five toes in the front-limb and four in the 

 hind, the hallux being the only aborted toe. In each the 

 under-surface of the toes has a series of " pads " or callosities, 

 consisting of a large middle one and a row of smaller ones. 



Coming to details, the scapula of the dog is slightly 

 elongated, but broad, with about equal prescapular and 

 postscapular fossae. It is distinctly a '' transition " type. 

 There is no clavicle, except for an occasional minute trace. 

 The humerus is curved and there is a large supratrochlear 

 foramen. The radius and ulna are both developed but 

 immovably fixed together. The carpus has the scaphoid 

 and lunare united to form one bone, the scapholunar (a 

 carnivore feature), hence there are, with the pisiform, only 

 seven carpal bones. The pollex is shorter than the other 

 four toes and does not reach the ground. Hence the animal 

 really w^alks on four toes in fore- and hind-limb. The last 

 phalanges bear small blunt claws which are not retractile. 



In the hind-limb and girdle the pelvis is not unlike the 

 ungulate type, but the ilium has not two " angles " or pro- 

 cesses, as in the horse and ox, as the " angle of the croup " is 

 very small. The femur is long and curved, the tibia and fibula 

 are also proportionately long, and the latter is complete 

 though thin. There is no reduction of the tarsal bones, and, 

 as stated above, there are four functional toes. The hallux is 

 often represented by a metatarsal bone, and may, as in the 

 " dew-claw " of domestic dogs, be present as a small digit. 

 The claws resemble those of the front-limb. In the cat 

 there is a clavicle which is reduced in part and connected 

 only by cartilage to the scapula and the sternum. The 

 scapula has a metacromion barely present in the dog. The 

 humerus is similar to that of the dog but proportionately 

 longer. There is no supratrochlear foramen, but there is 

 an entepicondylar foramen on the inner side. The radius 



