1913-] PATON— NERVOUS SYSTEM. 489 



as the work carried on by Coghill, which will unquestionably form 

 a basis for future studies of importance.^ Some of the results of 

 my own observations along these lines have been referred to in three 

 papers.- 



Before attempting to continue the description of the details of 

 my own investigations I wish to call attention to the variety as well 

 as importance of the problems awaiting solution in this special field 

 of enquiry. Many problems of phylogeny naturally suggest the 

 consideration of questions relating to the correlation of structure 

 and function. We find a parallel for the succession of events in 

 racial development in the ontogenetic sequence or the life-history 

 of the individual, in which are revealed a chain of phenomena much 

 better adapted for detailed study than those occurring in the former 

 and, what is of still greater importance, is that the latter are to a 

 certain extent under the control of the investigator. The compara- 

 tive rapidity with which individuals pass through the various stages 

 in development is also a factor facilitating enquiry. 



What is particularly needed at present is a careful systematic 

 study of the initial responses in the lives of embryos, representing 

 several different species of animals, and a record of these phenomena 

 which is sufficiently detailed to indicate the relationship existing 

 between the physiological events and the changes taking place within 

 the nervous system. Unfortunately investigators have long been 

 hampered by the compelling desire to attempt to solve the problems 

 relating to the complex nervous system of the adult before consider- 

 ing the simpler correlations possible in the early life of the embryo. 



Among the primitive adjustments of all organisms those for 

 temperature variations naturally play a very important role, and 

 this is only what might be inferred when we reflect upon the fact 

 that the responses of living beings to heat and cold are fundamental 

 properties of all living matter. The reactions recurring in response 

 to thermic stimuli, before the development of the nervous system, 

 present some interesting features. It has long been known that 



^ /. Comp. Neurol., Vol. 19, 1909. 



^ Mittheil. a. d. Zoolog. Station, 2, Neapel, 18 Bd., 2-3 Hft., 1907; /. Comp. 

 Neurol., Vol. 21, No. 4, August, 1911; /. Experiment. Zool., Vol. 11, No. 4, 

 Nov., 191 1. 



