26 PIGMENTARY GROWTH AFTER ABLATION OP 



the severed nerve termination. This would appear to be the 

 case, since if this atypical condition exhibited by the cells of 

 the normal graft to the albinous host was due to the action of 

 the tissue fluids upon the severed motor connections, we would 

 expect a change in the size of these cells in that interval which 

 must occur between the degeneration of this nerve ending and 

 the reestablishment of a new nervous connection, a change which 

 apparently does not occur. Because of the known potency of 

 minute amounts of endocrine secretions, the most natural as- 

 sumption is that this alteration has been effected through some 

 ' hormonal ' component of the plasma or lymph. 



Rather interesting results have been secured by submitting 

 these operated animals to adrenalin and to 'light and heat' 

 stimuli. These experiments, although not as complete as could 

 be wished, have been carried out on some half-dozen albinous 

 and normal tadpoles into which grafts from the opposite type 

 of animal had been made. The response or failure to respond 

 in the case of host and transplant cells has been nearly identical. 

 The tests were carried out from twelve hours to three days 

 subsequent to the operation and supply additional evidence 

 that the effective force causing a response of these cells to stimuli 

 is the direct application of the internal secretory substance to 

 the cell bodies and is not effected through the motor sympa- 

 thetic endings, since it is probable that any nerve ending severed 

 as it is from the nerve fiber would have degenerated in this 

 interval, and even after this lapse of time new connections could 

 hardly have been established. 



Some rather significant evidence has been secured on the 

 formation and migration of the epidermal melanophores in the 

 transplants. There invariably occurred an early migration of 

 the epidermal melanophores from the normal host into or over 

 the albinous transplant. In a period of a few hours the sulcus 

 intervening between the two types of skin would become filled 

 with a dense mass of melanin-rich cells in which the pigmented 

 epidermal cells could not readily be distinguished from the true 

 melanophores. In twelve hours, or even less, growing points 

 would appear from this confused scar tissue which invaded or 



