40 SKETCH OF THE ANATOMY OF THE HORSE. 



consequently gives them a high and thick crest (Fig. 312). The 

 intestines of the horse are supported by the abdominal tunic, which 

 covers the muscles of the lower part of the belly, and consists of 

 a broad, strong sheet of yellow elastic tissue. It acts like an elastic 

 abdominal belt. 



There is considerable power of movement between the head and the 

 first vertebra of the neck (the atlas), and between the different neck 

 vertebra themselves ; but hardly any between the dorsal vertebrce. The 

 Loin vertebrce can be flexed and extended to a slight degree on each other ; 

 but are capable of only very little motion from side to side. The 

 sacrum, as before mentioned, forms in the adult horse a single bone, 

 on which the pelvis rests, and with which it is connected by powerful 

 ligaments that greatly restrict its movements on the spine. We have 

 also seen that the thigh bones articulate with the pelvis. The joints 

 of the tail possess considerable mobility. The solid connection thus 

 afforded to the hind limbs, with the trunk, enables the former to transmit 

 to the latter the forward impetus given during progression with the least 

 possible loss of power. The capability of the loins to be flexed and 

 extended is necessary in order to faciHtate the action of the loin muscles, 

 which are important agents in locomotion (p. 67). The mobility of the 

 head, neck, and, to a much lesser degree, of the tail, acting as they do 

 as balancing poles, is extremely useful in enabling the animal to perform 

 with ease and precision many of the varied and difficult movements 

 demanded of him. We may see that any power of lateral motion which 

 the trunk (not counting the head, neck and tail) may possess, however 

 much it may make the horse quick and " handy " at turning, will mihtate 

 against his speed in a forward direction. 



The respective ends of the first eight ribs form movable joints with 

 the spine and breast-bone ; the first articulating with the last neck 

 vertebra and first dorsal vertebra ; the second with the first and second 

 dorsal vertebrae ; and so on. They are rigidly connected to their carti- 

 lages, of which those of the first eight, or true, ribs form movable joints 

 with the breast-bone.. Commencing from the spine, " the ribs pass 

 outwards and backwards, and then in an arched direction downwards, 

 their cartilages inclining inwards and forwards " {Strangeways). Owing 

 to the peculiar manner in which the ribs are curved, and to the fact 

 that the ends of the true ribs can pivot round in the joints which they 

 form with the spine and breast-bone, while the false ribs also form 

 movable joints with the spine ; the capacity of the chest is capable 

 of becoming much enlarged, when the middle portion of the ribs are 

 pulled forward by muscles that are attached to them. The mobility 

 of the ribs, which is all but absent in the first one, gradually increases 

 as they go backwards. They also increase in rotundity in the same 

 manner, the first one being the flattest. The first rib is the shortest, 



