PHAKMACOLOGY OF HYPOPHYSEAL EXTRACTS 753 



standard relation that has been adopted is that a solution of posterior 

 lobe extract in one to twenty thousand dilution shall give an equivalent 

 contraction effect as measured by the height of the line traced by the point 

 of a lever on the blackened surface of a kymograph as is obtained from 

 a similar amount of a one to twenty million dilution of pure crystalline 

 P-iminazolylethymin hydrochloric!. The method in general consists in sus- 

 pending an isolated uterine segment from a virgin guinea-pig in a glass 

 cell containing Ringer's solution through which a stream of oxygen is 

 continually passing, and surrounded by a bath kept constantly at body 

 temperature; the segment is so attached to a writing lever that a record 



Fig. 3. Showing the oxytocic effect of posterior lobe extract on the uterus in situ 

 and the similar type of response induced by histamin. (After Jackson and Mills. 

 J. Lab. & Clin. Med.) 



can be made of its movements. Apparatus for use in this test has been 

 devised by Roth (1914), Pittenger (1918), Hammett (1921) and others, 

 That of the latter is probably as simply constructed as any. When the 

 uterine segment has shown by its rhythmical contractions that it is in 

 a suitable condition for use, the height of contraction induced by the 

 previously mentioned dilutions of the standard and the extract to be 

 evaluated are compared and the results deduced therefrom. Of late it 

 appears as if the manufacturers of this product have succeeded in get- 

 ting a more potent extract that is frequently several times stronger than 

 the IT. S. P. requirements. Pittenger (1917), Pittenger and Vander- 

 kleed (1917), and Eckler (1917) have called attention to this and sug- 

 gested that the official requirement be altered. 



Another method of testing the efficacy of posterior lobe extracts is that 

 of measuring the rise in blood-pressure induced in an experimental animal 

 by the intravenous injection of the extract. This method is advocated 



