134 CALVIN P. STONE 



the initial copulatory act. Since they responded to the move- 

 ments of the receptive females by pursuit and mounting, it is 

 evident that visual stimuli were not necessary for the perception of 

 these characteristic movements. The age at which copulation 

 began is within the limits of variability for normal males (table 

 12, p. 127). The number of copulations of each animal during 

 twenty or thirty minutes following the first act gives no indica- 

 tion of handicap either in potency or in ability to find the female 

 in the cage (table 13, p: 128, rats 26 and 27). The copulatory 

 record of no. 27 during twenty minutes exceeds that of any other 

 animal tested in the laboratory. No experimental data is avail- 

 able to indicate to what degree vision is used in locating other 

 animals of the same species or in differentiating animals of the 

 same sex. In the above experiment neither of these functions 

 was called for because of the condition of confinement during 

 the observation. Casual observation of cage activities of rats of 

 various sizes has led to the impression that rats from forty to 

 fifty days of age have acquired habits of responding to the size 

 of other animals without first coming into physical contact with 

 them. If this impression is true, one might expect to find that 

 the blind young males might be much less aggressive in their 

 natural habitat if forced to compete in sexual activities with 

 larger males because of the tendency of the larger to dominate 

 the smaller. The dominating habits of the larger males might 

 bring about an accentuation of the fear and defense response in 

 the presence of other animals of either sex which would effec- 

 tually shunt all congenital sexual responses. 



B. Olfaction. It is generally believed that the sense of smell 

 plays a very important part in the excitation of sexual response 

 in various kinds of animals. This belief is founded upon the 

 observation of males smelling the external genitals of females 

 prior to copulation. In the case of the rat, vaginal smelling is a 

 practice so common that different investigators have considered 

 it an "excitant" to sexual activity. Thus Steinach (10) in 

 discussing the arousal of the sexual impulse in rats assigned to 

 the olfactory sense the function of setting the neural mechanism 

 concerned with the copulatory act into activity after it has been 



