PARS INTERMEDIA AND PARS TUBERALIS 



chromatosome-dispersing hormone is related to pigmentation 

 in mammals. 



Zondek (1935) reviews the clinical evidence in favor of the 

 view that extracts of the pars intermedia may cause anti- 

 diuresis in cases of diabetes insipidus. 



The assay of hormone{s) causing dispersion of chromato- 

 somes. — The assay of the hormone affecting the melano- 

 phores of the frog has been carried out by means of injections 

 into intact frogs or toads (Hogben and Winton, 1922-23; 

 Hogben and Gordon, 1930), by perfusing the hind limbs or 

 a greater portion of the body (Fenn, 1925; Krogh, McLean), 

 and by immersing isolated frog skin in a solution of the ma- 

 terial to be tested (Trendelenburg). If reliability is taken 

 into account, the last-named method appears to be the most 

 sensitive and, according to Jores, can be employed with a 

 maximum error of 25 per cent. 



Zondek and Krohn have described a method of determin- 

 ing the presence of the erythrosome-dispersing hormone by 

 observing the effects of solutions injected into P. laevis. 



From all the preceding discussion it is apparent that 

 changes in the melanophores of fish or frogs cannot be used 

 as a means of assaying the active principles of the pars 

 neuralis as was proposed by Spaeth (191 8), Loewe and 

 Ilison (192^;), and Treuter (1925). 



Does the pituitary secrete more than one hormone affecting 

 the chromatophores? — This question has been raised by 

 Jores'^ who has concluded that the substance causing melano- 

 some dispersion (frog) is different from that producing 

 erythrosome dispersion {Phoxinus). The distribution of the 

 "hormones" in the pituitary of the ox is said to differ. How- 

 ever, differences which are not great are difficult to evaluate 

 because of possible postmortem diffusion and because of the 

 errors of assay. Jores and Will concluded that "activation" 

 of the erythrosome-dispersing hormone is accomplished by 



'5 Jores and Lenssen (1933); Jores (1934); and Jores and Will (1934). 



