THE PITUITARY BODY 



relative dose of i). The results, in which the relative dose is 

 given first, and the gain in weight expressed in grams second, 

 were as follows: i : 22; 2:36; 4:36; 8 141; and 16:46. Such re- 

 sults would seem to indicate that their method, as routinely 

 used, has very little quantitative value. 



The hypophysectomized rat, operated upon when young, 

 responds much better to a growth-promoting extract than 

 does the normal young adult female rat. The difference be- 

 tween the responses of groups of the two types of animals is 

 not great if the comparison is made several months after 

 operation. Collip, Selye, and Thomson (1933) performed 

 their assays in recently hypophysectomized rats which they 

 preferred not to use repeatedly for such a purpose. They de- 

 fined their "unit" as the amount of hormone, administered 

 in I day, required to produce an increase of 15 g. in weight in 

 a period of 15 days. They used groups of six animals. 



The preparation and properties of growth-promoting extracts 

 of the pars glandularis. — Despite numerous attempts, the 

 growth-promoting hormone has been only imperfectly puri- 

 fied.''' It appears to be a protein or a protein-like substance. 

 The initial extraction of the hormone to produce a crude ex- 

 tract — by using either the fresh pars glandularis of the ox or 

 the same tissue after dehydration by means of acetone, re- 

 moval of the acetone, and powdering ("acetone powder") — 

 is best done in a dilute aqueous solution of an alkali. One of 

 the following alkalies is most frequently used: NaOH, 

 NHPH, Ba(OH)„ or Ca(OH),. If the extraction of the 

 glandular tissue is undertaken in the presence of even a very 

 low concentration of acid (pH 6.0), little or none of the hor- 

 mone can be detected in the fluid after extraction. 



Subsequent purification of the hormone contained in the 



'^ Evans and his co-workers (1921-22, 1924, 1928-29, 1933); Putnam, Teel, and 

 Benedict (1928); Hewitt (1929); Teel (1929); van Dyke and Wallen-Lawrence 

 (1930); Bugbee, Simond, and Grimes (1931); Wadehn (1932); and Collip, Selye, and 

 Thomson (1933). 



1 106I 



