THE PITUITARY BODY 



hatching. Subsequent work, principally by Riddle and his 

 collaborators, has also shown that this effect is probably due 

 to the hormone causing lactation in mammals. At least there 

 is evidence in favor of this view and none against it. 



THE EFFECTS OF THE LACTOGENIC 

 HORMONE IN BIRDS 



The effects of the lactogenic hormone on the crop glands of 

 the pigeon. — Extracts of the pars glandularis appear to stimu- 

 late the growth of the crop glands independently of their 

 effects, if any, on growth, on the gonads, and on the thyroid. 

 Similar extracts of other tissues have no effect on the crop 

 glands (Riddle, Bates, and Dykshorn, 1933). The hormone 

 which stimulates the development of the crop glands appears 

 to be identical with that causing lactation in suitable mam- 

 mals (De Fremery, Spanhoff, and Tausk, 1933; Riddle and 

 others, 1933; Anselmino and Hoffmann, 1934). 



Riddle and Braucher (1931) found that a macroscopic 

 growth of the crop glands could be observed about 3 days 

 after the injection of an anterior-lobe extract. One or 2 days 

 later, typical "crop milk" was present. The same effects were 

 produced on the denervated crop gland. Riddle and his col- 

 leagues stated that they produced crop-gland growth by in- 

 jecting the hormone into a hypophysectomized pigeon. The 

 crop glands of mature birds can be stimulated by \-\ the 

 dose of lactogenic hormone required for immature birds. 



Provided that the pure lactogenic hormone — when or if 

 it is isolated — produces, like extracts, lactation in mammals 

 paralleling the growth of the crop glands, it appears that the 

 latter effect is the more suitable basis for assay. In the first 

 place, assay in the pigeon requires the exercise of only a few 

 simple precautions, whereas in the mammal, assay can be 

 performed only after the animal has been suitably prepared. 

 Second, no attention need be given to the sex of the pigeon; 

 to use the male mammal, however, preparation for assay 



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