Regeneration 157 



acted as a regulator of the phenomena of metamor- 

 phosis in animals, but it was possible to show by simple 

 experiments that the central nervous system does not 

 play this r61e and that the regulator must be the blood 

 or substances contained therein. In the metamorphosis 

 of the Amblystoma larva the gills at the head and tail 

 undergo changes simultaneously, the gills being ab- 

 sorbed completely. The writer showed that in larvae 

 in which the spinal cord was cut in two, no matter at 

 which level, the sympathetic nerves were in all prob- 

 ability also cut the two organs continued to undergo 

 metamorphosis simultaneously. x Uhlenhuth found that 

 if the eye of a salamander larva is transplanted into 

 another larva the transplanted eye undergoes its 

 metamorphosis into the typical eye of the adult form, 

 simultaneously with the normal eyes of the individual 

 into which it was transplanted. 2 These and other 

 observations of a similar character leave no doubt that 

 substances circulating in the blood and not the central 

 nervous system are responsible for the phenomena of 

 growth and metamorphosis. 



An interesting observation on the r61e of internal 

 secretion in growth was made by Leo Loeb. 3 When 



1 Loeb, J., Arch.f. Entwcklngsmech., 1897, iv., 502. 



2 Uhlenhuth, E., ibid., 1913, xxxvi., 211. 



3 Loeb, Leo, ZentralbL f. allg. Path. u. path. Anat. t 1907, xviii., 563; 

 Zentralbl. f. Physiol., 1908, xxii., 498; 1909, xxiii., 73; 1910, xxiv., 203; 

 Arch. f. Entwcklngsmech., 1909, xxvii., 89, 463; Jour. Am. Med. Assoc., 

 1908, 1., 1897; 1909, liii., 1471. 



