674 TEXTBOOK OF ZOOLOGY 



facial bones enlarge, particularly in the ridges above the eyes, the 

 nose, and the lower jaw, and the soft tissues of the face undergo an 

 overgrowth resulting in a coarsening of the features. The hands 

 and feet may enlarge, also. The disease may prove fatal if it con- 

 tinues sufficiently long. 



A second hormone secreted by the anterior lobe has a direct in- 

 fluence on the sex organs. This hormone, prolan, stimulates growth 

 and activity of the gonads, the testes and ovaries, and therefore 

 controls the production of the gonadal hormones, which will be 

 discussed later. The absence of prolan results in an atrophy of the 

 testes and ovaries, and the cessation of the production of the sper- 

 matozoa and the ova; its injection increases the activity of the sex 

 organs. 



The posterior lobe of the pituitary also produces more than one 

 hormone, although pituitrin is the one concerning which we have 

 the most definite knowledge and which is commonly associated with 

 this portion of the organ. Pituitrin is known to stimulate the mus- 

 cles of the arterial system, increasing or decreasing the blood pres- 

 sure according to the amount of the hormone released in the blood. 

 It is also a stimulant for the musculature of the uterus and the 

 intestinal muscles. 



It is concerned also with the regulation and disposal of carbo- 

 hydrates in the body. The body is able to use an increased quantity 

 of sugar when the secretion of pituitrin is reduced; and, on the 

 other hand, when the quantity of the hormone is more than normal, 

 the body needs less sugar; carbohydrates not actually needed are 

 stored as fat, resulting often in abnormally fat people, extreme cases 

 of which are seen in the circus. The posterior lobe of the pituitary 

 probably does not affect the development of the bones, but the func- 

 tion just discussed is quite definite. 



The posterior lobe of the pituitary is concerned also with the 

 regulation of the secretion by the kidneys. A diseased condition, 

 known as diabetes iTisipidus, in which the patient voids large quan- 

 tities of urine, is treated by injection of the postpituitary hormone. 

 It appears that the hormone probably enables tissues to utilize and 

 store larger amounts of water than is possible in its absence. 



Still another effect of the secretion is found in the case of certain 

 amphibians and reptiles ; that is, its effect on the pigmentation of 

 the skin of these animals. The removal of the pituitary gland of a 



