The Two Components of Semen 27 



an increase or a decrease in spontaneous contractions. Cockrill, 

 Miller and Kurzrok (1935) observed that those specimens of human 

 semen which were capable of enhancing uterine contraction, caused 

 an inhibition after having been exposed for half an hour to pH 10; 

 at pH 11 all specimens became inactive. Moreover, the effect was 

 potentiated by eserine and suppressed by atropine. The observed 

 action corresponded to that of about 100 ^g. acetylcholine per ml. 

 semen. About that time, the occurrence of a powerful oxytocic 

 substance in the human seminal plasma was demonstrated by Gold- 

 blatt {\92>5b) who also found that the activity was destroyed by 

 short boiling of the seminal plasma with either OlN-NaOH or 

 OlN-HCl. When assayed on the guinea-pig's uterus, 1 ml. of human 

 seminal plasma showed approximately the same oxytocic activity 

 as 0-4-0-6 mg. of histamine. Euler (1937) believes that the oxytocic 

 activity is due to prostaglandin which in his experiments stimulated 

 strips of human uterus and also isolated uterus as well as uterine 

 strips from several species including the cow, rabbit, guinea-pig and 

 rat. Asplund (1947) determined the total content of 'contractive sub- 

 stance' in 155 specimens of human semen which he assayed on the 

 rabbit intestine in vitro, with purified prostaglandin as the standard. 

 He came to the conclusion that the effect of semen on the isolated 

 intestine must be attributed to a combined action of prostaglandin, 

 choline, and at least one other substance which produces a very 

 rapid increase in tonus and is unaffected by atropine. There was no 

 correlation between the total content of 'contractive substance' in 

 seminal plasma and the motility and viability of spermatozoa. 



In addition to the remarkable vaso-dilation and contraction of 

 plain muscle, the seminal plasma and the accessory gland secretions 

 exhibit a characteristic pressor activity towards blood vessels. In 

 1906 Jappelli and Scafa found that parenterally administered extracts 

 of the canine prostate produced an increased blood pressure in the 

 dog and stimulated the respiration. A similar effect was observed by 

 Thaon (1907) after the intravenous injection of prostatic extracts into 

 rabbits but in his experiments the rise in blood pressure was usually 

 followed by a fall. There are indications that the pressor action of 

 the prostatic extracts is due to adrenaline-like substances demon- 

 strated in semen and accessory glands by CoUip (1929), v. Euler 

 (1934Z>), Bacq and Fischer (1947), and Brochart (1948fl) (see p. 181). 



