DOMESTIC ANIMALS 



17 



the collar bone is absent. In fowls all 

 three bones of the shoulder girdle are 

 well developed, the collar bone being rep- 

 resented by the "wish bone." 



The pelvic girdle also consists of three 

 bones on either side, viz : ilium, ischium, 

 and pubis. The first two are directly- 

 articulated to the spinal column while 

 the pubic bones of either side unite be- 

 low to complete the arch. The three 

 bones of each side of the pelvis are pres- 

 ent in all of our domestic animals in- 

 cluding the fowls. 



Legbones of farm animals — There 

 is one formula for the bones of the 

 fore and hind legs of farm animals. 

 The first segment is a single bone, the 

 humerus of the fore leg, femur of the 

 hind leg. In the next segment there 

 are two bones; radius and ulna in the 

 fore leg, tibia and fibula in the hind leg. 

 In the dog, cat and Belgian hare the 

 radius and ulna are both well developed 

 and distinct. In ungulates the humerus 

 is short and stout while the ulna is com- 

 plete in the pig, rudimentary and be- 

 hind the radius in ruminants and firmly 

 united with the radius in the horse. 

 Similarly with the hind leg the fibula is 

 a complete bone in the pig while in the 

 horse there is merely a rudiment of it, 

 attached to the tibia. 



The original type of the mammalian 

 skeleton has undergone the greatest 

 modification in the bones of the feet. 

 In the horse there are only six of the 

 original ten wrist or carpal bones and, 

 since there is but one of the original five 

 toes, the horse has also but one meta- 

 carpal or cannon bone. Splint-like 

 rudiments of two other metacarpal 

 bones are to be found at the upper end 

 of the cannon bone or at the "knee" 

 joint. Below the cannon bone and form- 

 ing the shaft of the foot we have the 

 small cannon bone, coronary bone, and 

 coffin bone — the last being within the 

 hoof with the navicular bone behind it. 

 The stifle joint of the horse corres- 

 ponds to the knee of man. The "knee" 

 of the horse's fore leg corresponds to the 

 hock of the hind leg, both being at the 

 upper end of the cannon bone. The 

 fetlock joint is between the large and 

 small cannon bones, the pastern joint 

 between the small cannon or large pas- 

 tern and coronary or small pastern 

 bones, and the coffin joint between the 

 coronary and coffin bones. The horse 

 walks upon what corresponds to the nail 

 of the middle finger and middle toe of 

 man. 



In pigs four digits touch the ground, 

 the first being absent and the third and 

 fourth larger and in front of the second 

 and fifth. In ruminants the third and 

 fourth digits reach the ground while the 

 second and fifth do not. In dogs the 

 first digit appears on the side of the leg, 

 not in contact with the ground. 



In fowls the wing, which corresponds 

 to the foreleg of mammals, shows a well 

 developed humerus, radius and ulna, 

 while only one carpal and one metacar- 

 pal bone remain, along which the wing 

 feathers are attached. In the leg the 

 femur and tibia are strong bones but 

 the fibula is a mere splint. The tarsal 

 bones are absent while the shank con- 

 sists of a metatarsal bone (really three 

 bones fused together) to which the 

 four toes are articulated. 



The muscular system of farm animals 

 is too elaborate, the number of muscles 

 too great, and their modifications for 

 different purposes too complex for con- 

 sideration in detail in the present vol- 

 ume. All muscles are either striped or 

 unstriped (as examined under the micro- 

 scope) according as they are under the 

 immediate control of the will or not. 

 The heart muscle forms an exception 

 for it is striped though involuntary. 

 The essential characteristic of muscle 

 fibers is contractility which they possess 

 in high degree. The typical striped 

 muscles are concerned in locomotion, 

 being attached at either end to a bone 

 and extending across some movable 

 joint. The most important unstriped 

 muscles are found in the walls of the 

 intestines and blood vessels. (See 

 colored plates for location and names of 

 muscles.) 



Similarly with the nervous system, i n 

 so far as our present purposes are con- 

 cerned, it may be disposed of in a few 

 words. The central nervous system con- 

 sists of a brain and spinal cord. The 

 microscopic elements of this tissue are 

 peculiarly modified cells consisting of a 

 central body from which fibers run in 

 two or more directions. The cell bodies 

 constitute the gray matter, and the 

 fibers the white matter of the brain and 

 spinal cord. The gray substance is in- 

 side the spinal cord and on the surface 

 of the brain, constituting the cortex. 

 The most important parts of the brain 

 are the cerebrum, optic lobes, cerebellum 

 and medulla. There are twelve pairs 

 of cranial nerves originating in the 

 brain and controlling the special senses, 

 movements of the face, respiration and 



