122 CALVIN P. STONE 



by some animals at all during the periods of observation (Lt. 

 Elbow, tables 2 to 11). 



b. Acts that appear to be related to the copulatory act. At 

 all ages the young animals stop any activity in which they are 

 engaged to bite and scratch parts of their bodies. The amount 

 of scratching varies from day to day and shows no regular tend- 

 ency to increase or decrease at particular ages. Associated 

 with scratching of the body is the nibbling of the external 

 genitals which, in the case of the males, eventually comes to be 

 chiefly the licking of the penis. The amount of licking of the 

 genitals increases in amount from the age of thirty-five to forty 

 days and is seen frequently thereafter until the age of puberty 

 is reached. Casual observations lead to the conclusion that it is 

 continued throughout the period of potency of the male. In 

 the case of rat 52, a well developed male for his age, about 2 mm. 

 of the glans penis was seen protruding from the prepuce at the 

 age of forty-two days while the male was vigorously licking and 

 nibbling the sheath, using his fore-paws at the time to manipu- 

 late the organ into positions favorable for licking. With age 

 the tendency for the penis to protrude while licking becomes 

 greater because of development in size. Thus, accidentally 

 at first, the tongue is brought into contact with the sensitive 

 glans penis. The stimulating effect of licking probably causes 

 the act to be repeated and to become habitual. Whether 

 or not this act may be considered a form of masturbation in the 

 rat is an open question. It is well known that the tongue and 

 oral mucosa in contact with the penis of man is capable of arousing 

 the reflexes concerned with ejaculation. (Ellis, vol. 1.1.) In the 

 case of the rat, however, no case of orgasm has been discovered 

 as a result of the licking of the organ, but the difficulties of detect- 

 ing the orgasm are such that one cannot be sure that it is not 

 effected. The vigorous movements of the pelvis seen in some 

 instances of the licking and the use of the fore-paws to manipulate 

 the sheath suggest that these acts aid in producing the maximum 

 stimulation of this organ while licking is in progress. No evi- 

 dence was found which indicated that it aids in the initiation of 

 the first copulatory act. 



