Action of Epinephrin on Guinea-pig Uterus. 127 



non-pregnant and pregnant uteri of some animals may really be 

 due to a relative increase in the development of the circular 

 fibers. On the uterine horn in early pregnancy, epinephrin also 

 caused relaxation. Circular strips contracted. Later in preg- 

 nancy the circular fibers gave a more marked response. On 

 longitudinal strips taken from the same horn, epinephrin caused 

 an increased tone with increase in number and strength of what 

 Pettenger calls the "remittent contractions," but a suspension of 

 what is called the intermittent contraction. Of course it is a 

 question whether the so-called "remittent contractions" are not 

 due to the presence of circular fibers. Direct inspection of the 

 pregnant uterus in situ showed that epinephrin caused blanching 

 and constriction of the circular fibers, with probably relaxation of 

 longitudinal fibers. An oxidized solution of epinephrin, without 

 pressor action, made by passing air through a solution of epinephrin 

 for two days, caused marked increase in frequency of contractions. 

 Experiments on the longitudinal fibers (during late pregnancy) are 

 as yet incomplete, but would indicate that epinephrin caused 

 relaxation. 



