364 THE VERTEBRATE BODY 



dences of under-sexuality in the male may respond to this treatment. 

 It should be kept in mind, however, that the gonadotropic hormone does 

 not directly cause these changes, but stimulates the gonads to secrete the 

 hormones that cause them. 



The anterior lobe also secretes a lactogenic hormone that is necessary 

 for the secretion of milk in mammals and the associated mother instinct 

 necessary for nursing. By experimental use of this hormone a torn cat 

 has been made to secrete milk and nurse kittens. It may prove useful 

 in subnormal human lactation. 



A fourth hormone, the thyrotropic hormone, stimulates the thyroid 

 gland to produce thyroxin. Injection of extra quantities of this hor- 

 mone causes all the symptoms of hyperthyroidism and, if continued, an 

 increase in the size of the thyroid gland. 



A fifth hormone, the adrenocorticotropic hormone, generally re- 

 ferred to as ACTH, stimulates the secretion of the cortex of the adrenals. 

 It is often used rather than cortisone to alleviate the symptoms of 

 arthritis, since it stimulates a person's own glands to produce more 

 cortisone. Very good results have been obtained with it, but the effects 

 may wear off unless injections are continued. Unfortunately, too much 

 ACTH may lead to disturbed mental conditions and even insanity in 

 a few cases, so it must be used with caution. 



A sixth hormone, the diabetogenic hormone, seems to decrease sugar 

 metabolism ; thus it is directly antagonistic to insulin. Apparently it is 

 the balance between these that keeps the sugar level of the blood normal. 

 When the insulin decreases, this hormone causes the rise in sugar level 

 and diabetes results. Removal of the pituitary in experimental diabetic 

 animals has caused the sugar level of the blood to return to normal. 



REVIEW QUESTIONS 



1. Tell how the kidneys remove excretory wastes from the blood. 



2. Why do we say that frogs are like water animals with respect to reproduc- 

 tion? 



3. How do the eggs reach the oviduct in frogs ? How does this compare with 

 the method in human beings ? 



4. How do the endocrine glands differ from other glands in the body? 



5. Name the endocrine glands, tell what hormones they secrete, and give the 

 general function of each hormone. 



6. If a person having diabetes becomes greatly upset emotionally he may go 

 into a diabetic coma. Can you reason out why ? 



7. Gonadotropic hormone will cause precocious sexual development in normal 

 young animals, but not if the animals are first castrated. Explain. 



8. If the pituitary gland is removed from an animal showing symptoms of 

 diabetes the symptoms will disappear. Explain. 



9. Explain how the ducts leading from the kidneys differ in the male and female 

 frogs. 



10. What hormones have been beneficial in the treatment of arthritis? Why? 



