1176 



HORMONAL REGULATION 



lations and the activity culminating in these 

 ejaculations may be spread over as much 

 as 3 hours (Stone and Ferguson, 1940; 

 Beach and Jordan, 1956). A quiescent or 

 recovery period of 24 hours or more follows 

 (Stone, Ferguson and Wright, 1940), al- 

 though 5 or 6 days and even longer may 

 be necessary (Beach and Jordan, 1956; 

 Larsson, 1956). Beach and Jordan studied 

 the changes in behavior preceding each 

 successive ejaculation up to and including 

 the sixth. The number of intromissions be- 

 fore ejaculation decreased from an average 

 of 10.6 to 4.1. Ejaculation-latency (interval 

 from the first mount to ejaculation) de- 

 creased from an average of 450 to 132 sec- 

 onds. The refractory period (period of 

 sexual inactivity following all but the ter- 

 minal ejaculation) increased from an aver- 

 age of 324 to 818 seconds. 



Unless otherwise noted, the description of 

 the behavior shown by the male guinea pig 

 is taken from that given by Young and 

 Grunt (1951). When a female in heat is 

 placed with a male he begins to follow her 

 almost immediately, usually sniffing at the 

 anogenital region. This behavior is nuzzling. 

 Within a few seconds he may mount her, 

 usually posteriorly but often elsewhere. If 

 the forepaws are placed on the back of the 

 female without other contact, the act is 

 abortive mounting (Valenstein, Riss and 

 Young, 1954) , but if the back of the female 

 is covered it is mounting. ^Mounting may be 

 accompanied by pelvic thrusts without in- 

 tromission, but often it is followed by intro- 

 mission with or without pelvic thrusts. The 

 duration of intromission varies, depending 

 partly on the male and partly on the re- 

 sponsiveness of the female. Frequently she 

 withdraws from the male at the instant of 

 intromission, in which case there is no 

 opportunity for pelvic thrusts. More often 

 there is a series of pelvic thrusts lasting 2 

 to 5 seconds or more. Following intromission 

 of this type, males and females usually 

 clean the genitalia even though there was 

 no ejaculation. Ejaculation is known to 

 have occurred only if the final thrust is 

 conspicuously prolonged and accompanied 

 by a drawing in of the flanks as in a spasm ; 

 both animals then fall back on their 

 haunches and clean the genitalia. If the 



male is watched, he can be seen to drag his 

 butt along the floor of the cage somewhat 

 as a dog infested with worms will do. Dur- 

 ing the test a sniffing or nibbling at the 

 hair anywhere on the body of the female 

 may be seen. The element is designated 

 sniffing and nibbling. 



In the guinea pig, in contrast to the rat, 

 the single ejaculation usually marks the 

 end of any strong interest in the female; 

 in most tests it is accomplished within 10 

 minutes. If after ejaculation the first es- 

 trous female is replaced by a second, there 

 may be a revival of interest (Grunt and 

 Young, 1952c), but this feature of behavior 

 has not entered into the determination of 

 the strength of sexual behavior. Interest is 

 also restimulated in the male monkey by 

 the introduction of a second female (Car- 

 penter, 1942a) and in the bull by a change 

 of teasers (Cembrowicz, 1952; Almquist and 

 Hale, 1956). The presence of a new estrous 

 female does not have such an effect on a 

 satiated male rat (Larsson, 1956) . 



Ejaculation can be distinguished more 

 easily in the guinea pig than in the rat; in- 

 deed it was not until 1934 that ejaculation 

 was identified as a discrete element in the 

 rat (Stone and Barker, 1934). As recently 

 as 1946 Beach and Holz wrote, ''ejaculation 

 referred solely to observable mating reac- 

 tions," apparently without implication as to 

 the discharge of seminal fluid. 



These elements of the mating behavior 

 pattern, along with the length of the inter- 

 val between the beginning of the test and 

 ejaculation in the guinea pig, are the end 

 points that were used in the development 

 of the scoring systems now prevalent in 

 this country. The elements are given differ- 

 ent values in an ascending order. In the rat 

 the order is mounting and clasp-without- 

 palpation, mounting and clasp-with-pal- 

 pation and pelvic thrusts (referred to as 

 attempts by Stone, Tomilin and Barker, 

 1935 and as incomplete copulation by Beach 

 and Holz, 1946), copulation which consists 

 of mounting, palpation and pelvic thrusts 

 followed by the backward lunge signifying 

 that intromission has occurred, and ejacida- 

 tion. In the guinea pig the order is sniffing 

 and nibbling, nuzzling, abortive mounting 



