144 



The Endocrine Organs 



that of the uterus. One of these is a hormone, and either excites the muscle 

 to contraction or renders it more excitable to the natural stimuli which are 

 producing the contractions ; the other is a chalone, tending to prevent or 

 diminish the contractions. The difference of result obtained would depend 



uterus 



kidney 



carotid 



respira- 

 tions 



time in 10" 

 signal 



FlG. 99. Effect of intravenous injection of extract of corpus luteum on uterus, kidney volume, 

 blood-pressure, and respirations of cat. The small waves on the uterus curve are caused 

 by the respirations. 



uponthe relative amount of one or other autacoid in a particular extract, 

 and on the sensitiveness of the tissue under examination to the effects of 

 excitatory or inhibitory agents. Whether the action is exercised through 

 nerve end-organs, or whether it is a direct effect upon the contractile tissue, 

 is a point which it has not been easy to determine. 



On Milk Secretion. One of the effects of intravenous injection in 

 lactating animals of extract of corpus luteum is to provoke an outpouring 



