13— ANATOMY OF THE DOG 



walls of the bladder are Hsrht and transparent, 

 able to expand greatly and to hold a large 

 quantity of urine. 



"Stones" Grow from Within 

 Stones may form in the kidneys and bladder 



thru certain secretions, usually alkaline: these 

 stones may grow to an enormous size. Occa- 

 sionally they disintegrate but in most 

 must be removed by operation. 



VI. THE NERVOUS SYSTEM 



The "big chief" of the nervous system is, 

 of course, the brain, which functions thru the 

 medium of the nerves. The heart may supply 

 the life blood but the brain alone can super- 

 vise the movements and functions of the body 

 and all its parts. 



Two Groups of Nerves 



There are two parts of the nervous system — 

 central, which is made up of the brain and 

 spinal cord ; and the peripheral system, which 

 includes the nerves of the head and spine, and 

 the sympathetic nervous system. 



2 Functional Divisions of Nerves 



The nerves themselves divide into two 

 classes — the sensory or afferent nerves, which 

 carry impulses from the tissues to the brain. 

 All feeling, all awareness is recorded in the 

 brain in reality and not in the part of the 

 body which furnishes the sensation. The 

 sensory nerve carries the impulses from the 

 affected part to the brain. 



The "Boss" Nerves 



The second class of nerves are the motor or 

 efferent, which carry impulses from the brain 

 to the tissues, directing them what action 

 to perform. 



Two Parts of the Brain 



The brain is a mass of nerve substance oc- 

 cupying the cavity of the skull. The cere- 

 brum is the larger and more important part 

 and is divided into two by a central deep 

 fissure. 



The cerebellum is located behind the cere- 

 brum or brain proper. It has the appearance 

 of an English walnut, having many folds and 

 fissures. It is concerned mostly with the con- 

 trol of equilibrium. When a dog staggers or 

 walks unsteadily, the cerebellum likely is 

 affected. 



"Central" for Nerve Wires 



The spinal cord is a long mass of nerve 

 substance inside the backbone, running from 

 the head to the sacrum (rear base of tail). All 

 the nerves of the body run off from the spinal 

 cord with the exception of twelve, which 

 originate in the brain itself. 



The peripheral nerves divide and sub- 

 divide from the brain and the spinal cord so as 

 to communicate with all the body tissues. 

 Nerves and Heart Affect Each Other 



The sympathetic nerve system regulates the 

 supply of blood to the internal organs in that 

 it controls the contraction of the blood vessels. 



Vn. THE LYMPHATIC SYSTEM 



The lymphatic system is also known as the 

 absorbent system. In addition to the blood 

 there is another fluid called Ijmiph, and it cir- 

 culates thruout the entire body and all the 

 spaces of the tissues by means of its own com- 

 plete channels. 



Protector Against Body Poisons 



It assists in the absorption of the food ma- 

 terial, carries off excess material and absorbs 

 certain poisonous and waste products of these. 



Complete System of Its Own 



The Ijmaph drains out of the tissues thru 

 vessels similar to blood vessels. It is dis- 

 charged into the thoracic duct and from there 

 into the vein anterior vena cava, which in 

 turn discharges into the right heart auricle. 

 Thus the heart pumps both blood and Ijrmph. 



As the lymph absorbs toxic material, the 

 nearest lymphatic glands swell and become in- 

 flamed when infective material gains access 

 to tho circulation thru a septic wound. 



VIII. THE DUCTLESS GLAND SYSTEM 



The ductless glands are the spleen, thyroid, 

 thymiis, adrenals and pituitary bodies. They 

 secrete without any definite channels thru 

 which the secretions are conveyed away. 

 The Spleen a Mystery Gland 



The spleen is shaped like a sickle and is 

 attached to the stomach. Its exact function 

 is not clearly known altho it does break 

 down certain elements in the blood system. 

 Goiter and Th}rroid 



The thsrroid is situated on the windpipe close 

 to the larynx and consists of two lobes, one 

 on each side of the center line. Several 

 smaller bodies connected with the tiiyroid are 

 named parathsrroids. 



The thyroid produces a secretion which is 

 essential to the body, likely one which neu- 

 tralizes poisons. Goiter is a swollen diseased 

 condition of the thyroid gland. 



Another Mystery Gland 

 The thymus is situated on the floor of the 

 thorax (chest) in front of the heart. The 

 exact nature and function of this gland are 

 not known but when a young animal is cas- 

 trated, the gland does not atrophy and disap- 

 pear promptly as is the case when there is 

 normal reproductive activity. 



Stopping Internal Bleeding 

 The adrenals are two small oval bodies at- 

 tached to the kidneys. An extract from these 

 constricts small blood vessels and arrests 

 bleeding. 



Pituitary Near Brain 

 The pituitary is a small structure on the' 

 floor of the cranium beneath the brain. De-* 

 flciency brings on fatness and "foolish 

 actions." 



