40 THE ARMY HORSE. 



region, passes forward beneath the hunbar and dorsal vertebrae, 

 and empties into the anterior vena cava just in front of the 

 heart. 



Each of the villi of the intestines contains a minute vessel 

 called a lacteal, which absorbs chyle and receives its name from 

 the lacteal or milky appearance of that fluid. These vessels of 

 the smaller lymphatic system unite and form larger tubes 

 which empty into the rece-ptaculnm chyli (chyle reservoir), 

 which is a part of the thoracic duct of the larger system. 



It will thus bs seen that the lymph with its waste material 

 and the chyle with its nutrient material are mixed and poured 

 into the impure blood. The lymph and chyle are taken up into 

 the serum and tlie waste material is thrown off from the circu- 

 lating blood by the lungs, skin, and kidneys. 



Lymph, therefore, makes a circuit very much as blood does. 



To simplify the explanation of the system, the Ijanphatic 

 glands have not been mentioned. 



Glands are organs the function of which is to separate cer- 

 tain substances from the blood, which are either to be used in 

 the animal's system or to be thrown off as waste material. 



The lymphatic glands are so placed that the lymphatic ves- 

 sels pass through them in their course toward the main trunks. 

 These glands act as filters and remove any infective material 

 from the lymph and also supply lymph corpuscles, which are 

 identical with the white corpuscles of the blood. 



'\^^ien the glands are situated near diseased structures, an 

 amount of infected material lodges in the glands, greater than 

 can be overcome by the lymph corpuscles, and, in consequence, 

 inflammation and swelling of the glands result. 



ANATOMY OF THE NERVOUS SYSTEM. 



A nerve consists of a bundle of tubular fibers, held together 

 by dense connective tissue; the nerve fibers form a conducting 

 apparatus, to convey impulses of sensation and to transmit im- 

 pulses of motion. 



The nervous system is divided into two minor systems, the 

 cerebro-sj}inal, which is to a considerable extent influenced by 

 the will of the animal, and the sympathetic^ which is not di- 

 rectly influenced by the will. 



In the first the center is made up of two portions, the brain 

 and the spinal cord. 



