86 THE HORSE IN HEALTH AND DISEASE 



peripheral vein and caused death, while the same dose introduced 

 into the portal vein was without effect. 



Fats are absorbed only by the lacteals, but as fatty acids and 

 glycerin rather than true fats. They appear to be again converted 

 into fats by the action of the epithelial cells in the walls of the 

 intestine. Fats, like proteins and carbohydrates, are fuel foods, 

 and are used as a source of body heat and energy. Although they 

 are not carried directly to the liver, as are the proteins and carbo- 

 hydrates, they frequently are accumulated there until required for 

 use. Most cells and tissues of the body have the power to store 

 fats for future use. This function varies with the character of the 



THE DUCTLESS GLANDS AND THEIR FUNCTIONS 



The principal glands without ducts are the spleen, the thyroid, 

 the thymus, the adrenals, and the pituitary and the pineal bodies. 

 Little is known about the functions of these glands. In recent 

 years it has been found that they play important r61es in the 

 elaboration of the so-called internal secretions, which pass directly 

 into the veins or lymphatics instead of being conveyed away by 

 ducts. 



The spleen is a large vascular organ situated in the left portion 

 of the abdominal cavity. It is sickle shaped, weighs a little more 

 than 2 pounds, and averages 20 inches in length (Fig. 25). It 

 is bluish-red in color, and is soft but not friable in the natural 

 state. The function of the spleen is not positively known, but it 

 is supposed to have something to do with the formation and destruc- 

 tion of the red blood-corpuscles which are found in the organ in 

 great numbers. Animals live with little inconvenience when it is 

 removed. 



The thyroid gland is situated in the neck below the anterior 

 part of the trachea. It may be easily felt in the living horse. It 

 is very vascular, firm in texture, and dark red-brown in color. 

 Enlargement of the gland results in the disease termed "goiter." 

 An important internal secretion is produced by the thyroid, which 

 has to do with the process of nutrition. Animals live but a short 

 time after the gland has been removed. If they are fed on fresh 

 thyroid gland from another animal they seem to suffer no incon- 

 venience. 



The thymus gland is found between the heart and the larynx. 

 In late fetal life and the very young animal it is seen as a long chain 



