Crew and Wiesner affirm that "our own experiments show that not only is the metamorphic factor not identical with the growth hormone[long dash]as has been concluded by Spaul[long dash]but that it also differs from the gonadotropic hormones. It may be assumed, therefore, that a 4th anterior pituitary hormone ([theta]) exists. Further experiments will show whether it is thyreotropic, as it seems to be.