QUESTIONS AND ANSWERS 123 



covering. Valves, similar to the ones found in veins, are seen in 

 their interior. All the lymphatic vessels of the left side of the head 

 and neck, the left fore limb, the chest, the abdominal cavity and 

 hind limbs converge toward and empty into a central vessel, the 

 thoracic duct, which empties into the anterior vena cava; the 

 lymphatic vessels of the right side of the head and neck and the 

 right fore limb collect and pour their contents by a separate duet 

 into the same vein. 



What medicinal and other agencies may be employed as lympha- 

 gogues? 

 Ingestion of large quantities of water assists in increasing the 

 amount of lymph. Certain agents, when injected into the circu- 

 lation, increase the flow of lymph, such as peptone, decoctions of 

 intestinal wall, liver, etc., crystalline bodies such as sugar and 

 neutral salts. The administration of sodium citrate by the mouth 

 increases the general lymphatic circulation. 



In what diseases of connective tissue is the lymph specially involved? 

 In infected wounds and suppurative inflammations. 



What forces assist the flow of lymph? 



Contraction of vessel walls, aspiration by the diaphragm, con- 

 traction of the abdominal muscles, peristalsis, and valves in the 

 IjTnph-vessels. 



Skin 

 State the function of the skin. 



Protective covering for the body; sense of touch; excretion of 

 waste matter and regulation of temperature. 



Describe the glands found in the skin of domestic animals, noting 

 the relative nimiber and complexity of these in the different 

 genera, and the attendant variation of the product in amount 

 and facility of secretion. 

 The sweat-glands in the ox are rudimentary, consisting merely 

 of oval sacs found principally on the muzzle. In the horse, dog, 

 cat, sheep and hog they are more highly developed, being long 

 convoluted tubes which pass through the entire thickness of the 

 skin. The sweat-glands of the horse are quite generally distributed, 

 but there are certain parts of the skin which sweat more freely than 

 others, for instance, the base of the ears, the neck, sides of the chest 

 and the inside of the thighs. Mules and donkeys sweat with diffi- 

 culty and then principally at the base of the ears. Dogs and cats 



