20 INTRODL'CTION. 



The centre of almost all the bones is more or less hollow, and con- 

 tains marrow. This substance seems to be necessary to the health 

 of the bone, and it may be a reservoir of nutriment in case any parti- 

 cular state of the constitution should require it. 



The bones are covered by a membrane called the periosteum^ which 

 gives attachment or hold to the muscles by which the bones are 

 moved. The ends of the bones, forming the joints, are tipped with 

 cnrtiluge, which is a polished elastic substance, facilitating the mo- 

 tions of the heads of the bones upon each other, and preventing bad 

 effects from concussion. Still more to avoid friction or concussion, 

 these cartilages are lined by a membrane, which secretes an oily 

 fluid, — the joint oil or synovia. The heads of the bones are held to- 

 gether by ligaments, and thus joints are formed. These ligaments 

 are white, fibrous, and tough ; possessed of sufficient elasticity to 

 accommodate themselves to the various motions of the joints, but not 

 enough to endanger their strength. 



The Head. — The head, comprehending the skull and face of the 

 animal, is composed of numerous bones closely united to each other. 

 The skull contains and defends from injuries that important organ, 

 the brain; and in it are found four of the organs of sense, which 

 minister so much to the enjoyment of the animal, viz. those of hear- 

 ing, sight, taste, and smell. 



The Teeth. — Neat cattle have eight fore teeth in the lower jaw, 

 and none in the upper one : twelve grinders in the lower jaw, and as 

 many corresponding ones in the upper one. Each tooth has its body 

 and root : the body is all that part appearing without the gum, the 

 root or fang is covered by the gum, and lies deep in the bony socket. 

 The front teeth are composed of two substances, — the internal bony 

 part, and its covering, the enamel. This latter is exceedingly hard, 

 and gives to the front teeth their cutting edge. The sides of the back- 

 teeth are also covered with enamel, and columns of enamel are let 

 down iato the body of these teeth. While the bone is gradually worn 

 away, the enamel is scarcely touched, and so there is formed a rough 

 and uneven surface on the top of the grinders, admirably adapted for 

 breaking down the food. 



The teeth, although of firmer structure than the rest of the bones, 

 are also plentifully supplied with nerves and blood-vessels. 



How to ascertain the Age of Neat Cattle by their Teeth. — The calf is 

 \isudlly born with two fore or cutting teeth, and at a month old the 

 whole eight are cut. The age is then guessed at by the wearing 

 down of these teeth until the calf is eight months old, when they be- 

 gin to become narrower and smaller. At eight months the two centre 

 teeth are smaller than the rest; and from that time until eighteen 

 months the others gradually diminish, until the whole are very con- 

 siderably lessened in size and stand apart from each other. 



At two years old the two middle teeth are pushed out, and suc- 

 ceeded by two permanent ones ; at three there are four permanent 

 teeth ; six at four years ; and all the eight at five, when the animal 



