Effects of Extracts of Posterior Lobe of Pituitary 87 



choline, for it is not affected by atropine. In birds only dilatation of vessels 

 is produced, and this is antagonised by atropine (Noel Paton and Watson). 

 On the heart's action the repeat dose has the same effect as the first 

 dose, i.e. the beat is strengthened (Biedl). The effect on the uterus (see 

 below) is also repeated if administration of the autacoid is repeated. The 

 pressor effect and the effect on the heart produced by the stimulating 

 (hormonic) autacoid usually lasts a considerable time (a quarter to half an 



FIG. 58. Tracing to show the effect of the addition of extract of posterior lobe 

 of pituitary body to Ringer's solution in which a longitudinal strip of 

 intestinal muscle was suspended. (A. W. Young.) Notice both the increase 

 in force of the individual contractions and the increase in tone of the muscle. 



hour or more), varying, however, with the dose ; the depressor effect of the 

 chalonic autacoid has a much shorter period of activity. 



The extract of pituitary acts upon other plain muscular tissue besides 

 that of the blood-vessels. Thus it powerfully affects the bladder and 

 intestine (fig. 58) (Blair Bell and Hick), the stomach (Houssay), 1 the uterus 

 (fig. 59) (Dale), 2 even in minute doses ; it also produces dilatation of the pupil 



1 Houssay states that the secretion of gastric juice is at the same time increased ; this is 

 perhaps the result of setting up contractions in the muscularis mucosae. 



2 The uterus is also rendered more excitable to influences reaching it through its nerves. 

 According to Dale, pituitary extract acts on plain muscle more by increasing its sensitiveness 

 to normal stimuli than by acting as a direct excitant. Thus when administered in pregnancy 

 before the commencement of parturition it produces no effect ; whereas its action during 

 parturition is well established. Engeland and Kutscher claim to have isolated an autacoid 

 which affects the uterus only. 



