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 



'X^J-^-vsA'V 



respira- 

 tions 



time in 10" 

 signal 



u_i_L_L_LJ 



1 [ 1 II 1 



J 1 L 



Fig. 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. 



upon the 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 



