PARS GLANDULARIS AND LACTATION 



in about 20 per cent of the cells. According to Valle (1937), 

 smears of the cells of crop-gland secretion can be obtained 

 by means of a fistula. Especially 48-72 hours after the injec- 

 tion of lactogenic extract, the cells are found to contain 

 orange-colored droplets of various sizes after fixation in 

 formalin and staining by sudan III and methylene blue." 



The chemistry of the lactogenic hormone. — White, Catch- 

 pole, and Long (1937) recently described a method of isolat- 

 ing a crystalline lactogenic principle which presumably is the 

 pure hormone. By the two-day intracutaneous test of Lyons 

 and Page a "unit" was found to be 0.05-0.1 7; by a systemic 

 test, also in pigeons, o.i mg. was designated a unit. The 

 method used was briefly as follows: 100 mg. of purified ex- 

 tract was dissolved in 2 cc. of 13 per cent acetic acid to which 

 was added 2 cc. of 13 per cent pyridine. The cloudy mixture 

 was set aside and later centrifugated. The precipitate was 

 subjected to the same treatment — the whole process being 

 repeated ten times. Crystalline hormone was finally ob- 

 tained either by allowing the acetic acid-pyridine mixture to 

 stand in the refrigerator or by the careful addition of i per 

 cent NH4OH to the mixture followed by centrifugation and 

 refrigeration of the turbid mother-liquor. The crystalline 

 material yielded on analysis 51. 11 per cent of C, 6.76 per 

 cent of H, 14.38 per cent of N, and 1.77 per cent of S. It 

 appeared to be protein or protein-like. The following reac- 

 tions were positive: xanthoproteic, biuret, labile S, Millon, 

 and Hopkins-Cole. 



Other reports are of interest so far as the preliminary puri- 

 fication of the hormone is concerned.^-' The most varied 

 media have been used for initial extraction: 60-70 per cent 

 alcohol at "pH" 9-10 (this was used by Bates and Riddle 



"Leblond and Nelson (1937) and Leblond and Noble {1937), who injected ma- 

 terial intracutaneously, concluded that non-specific proliferation of the crop-glands 

 can be produced (e.g., by liver). In proliferation not due to lactogenic hormone, fat- 

 granules are not found in the growing epithelium. 



^3 Bates and Riddle (1935), Bergman and Turner (1937), Evans (i937)> Lyons 

 (1937), and McShan and French (1937). 



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