CHAPTER XI 



THE EFFECTS OF EXTRACTS OF THE PARS NEU- 

 RALIS ON THE CIRCULATORY SYSTEM AND ON 

 THE SMOOTH MUSCLE OF STRUCTURES SUCH 

 AS THE UTERUS AND THE BOWEL; OTHER 

 EFFECTS OF EXTRACTS^ 



FOLLOWING the announcement of Oliver and Schafer 

 in 1 894 that the intravenous injection of extracts of the 

 pituitary body causes a rise in the blood pressure, 

 Howell (1898) pointed out that the active substance is in 

 the posterior lobe. A more detailed analysis of the effects of 

 posterior-lobe extract on the circulation has been made dur- 

 ing the forty years following the discovery of Oliver and 

 Schafer — particularly since 1928 when the vasopressor and 

 oxytocic principles, as substances fairly completely separated 

 from each other, were made available for investigation. 



The effects of extracts of the pars neuralis on the circulatory 

 system. — The vasopressor principle causes an elevation of the 

 blood pressure by a direct effect probably on the smooth 

 musculature of the small arteries and the arterioles. There 

 also may occur, depending upon conditions, a constriction 

 of the capillaries and venules. The pressor effect can be pro- 

 duced in the absence of the adrenal glands or after the de- 

 struction of the central nervous system. It is not prevented 

 by substances which paralyze the peripheral terminations of 

 the sympathetic (ergotoxine, ergotamine) or parasympathetic 

 (atropine) nervous systems. Intramuscular or subcutaneous 

 injections sometimes have no effect or cause a slow rise in 

 blood pressure. If repeated doses are administered intra- 



' Detailed references to the earlier literature bearing on the subjects discussed 

 in chaps, xi and xii will be found in the review of Ceiling (1926) and in Sharpey- 

 Schafer's The Endocrine Organs (1926). 



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