96 CALVIN P. STONE 



nature of activating stimuli our knowledge is very incomplete. 

 For the most part investigators have dealt with the external 

 stimuli alone. They have overlooked the internal factors. 

 Now, to really understand the activation of native patterns of 

 response, it is necessary to take the latter into account as well; 

 for the external stimuli merely discharge the elaborate and com- 

 plex neuromuscular and glandular mechanisms pre-organized 

 by the action of potent internal factors operating within the 

 organism. A preliminary survey of the internal factors operat- 

 ing would seem to indicate that at least two distinct types can 

 be recognized. There is a group which underlies the develop- 

 ment and integration of the neuro-muscular and glandular mecha- 

 nisms, and another that serves to keep the mechanisms in a state 

 of readiness for response to particular patterns of external 

 stimulation. 



The field of congenital sexual activity offers a favorable oppor- 

 tunity for an intensive and comprehensive study of a type of 

 behavior both typical and universal. It is a type which may be 

 satisfactorily studied in the ordinary laboratory animals; and it 

 should yield data of both -theoretical and practical importance 

 for many general phases of congenital activity. On this account 

 congenital sexual behavior was subjected to experimental study 

 in this investigation. The study is concerned primarily with the 

 copulatory act of the young male albino rat. 



On the whole the rat is a very satisfactory animal for observa- 

 tion in a study of sexual behavior. It thrives well in confine- 

 ment, becomes sexually mature in a relatively short time (sixty 

 to ninety days), and displays its sexual behavior, under appro- 

 priate stimulation, throughout the entire year. The copulatory 

 act of the animal is one that may be studied from many aspects. 

 Its appearance in post-natal life is late enough to make possible 

 a genetic study of its development; and it persists throughout a 

 span of the rat's life sufficiently long to enable one to observe 

 the alterations with age, experience, and modified conditions 

 of the general metabolism. 



In this paper an attempt will be made to set forth salient data 

 concerning: (1) The constituent elements of the copulatory 



