ACTIVE PRINCIPLES OF PARS NEURALIS 



lature of the uterus, this phenomenon was soon employed 

 as a means of assaying posterior-lobe extracts. However, no 

 generally satisfactory method of quantitative assay was pos- 

 sible until the international standard powder became avail- 

 able. A salt of histamine, which was first recommended by 

 Roth (1914), is unsatisfactory not only because its pharma- 

 cological behavior is different (e.g., it causes a relaxation of 

 the rat's uterus) but also because the oxytocic effects of 

 extracts are quantitatively different if a histamine salt and a 

 posterior-lobe extract are compared as standards. 



Today the isolated uterus of the immature guinea pig im- 

 mersed in some modification of Locke's solution is most gen- 

 erally employed for the biological assay of the oxytocic 

 principle. An effort is made to cause equal and reproducible 

 (in the sense of equality of contractions) submaximal con- 

 tractions of the uterus both by the standard and by the un- 

 known extract. The details of technique vary considerably; 

 an example of a method widely followed is that of Burn and 

 Dale (1922).'' With good technique an assay may be per- 

 formed with an accuracy of +20 per cent. 



A study of the effects of changes in the ionic environment 

 on the contraction of the isolated guinea pig's uterus in re- 

 sponse to posterior-lobe extract was made by van Dyke and 

 Hastings (1927). (See also Martinescu and Popoviciu [1925] 

 and Salzberg [1931].) 



According to Trendelenburg (1928) and Penau, Prud- 

 homme, and Simmonet (1931), the isolated uterus of the 

 young sheep, although less sensitive than the guinea-pig 

 uterus, can be satisfactorily used for the assay of the oxytocic 

 principle. Schiibel and Gehlen (1928, 1933) recommended 

 that quantitative assay be performed in the puerperal cat 

 (2-4 days postpartum) by distending the uterus with fluid 



■^ For other reports on the technique of assay, see Trendelenburg and Borgmann 

 (1920); Trendelenburg (1922 and later); Kochmann (1921); Stern and Peyrot 

 (1921); Smith and McClosky (1924); Sawasaki (1925); Penau and Simmonet (1925- 

 26); Fromherz (1926); and GuUand (1933). 



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