MAMMALS 61 



with the usual condition in other animals, the important 

 point is the physiological effect of the habitual friction and 

 scratching on the skin and its blood-vessels. This is the point 

 which was overlooked by Von Fischer and by Darwin. The 

 effect on the individual has, after a great number of genera- 

 tions, been accumulated by heredity in the species. 



Von Fischer refers to a fact well known to everyone who 

 has much experience of dogs, that these animals also are very 

 fond of having their back and loins rubbed, that they not 

 uncommonly turn the hinder end of their bodies to persons 

 in their company inviting this action, and that the result of 

 the sensation is to excite their sexual feelings and sexual 

 organs. The comparison shows how naturally the habit 

 would have arisen and been carried to excess in the apes and 

 baboons, in which the nervous system is so much more active 

 and excitable. 



The drill on which Fischer made observations was a young 

 female, so that the redness of the buttocks and the gesture 

 described occur in this species in both sexes. The gesture is 

 especially exhibited during the rutting season. 



Darwin states that in Macacus rhesus the naked skin on 

 the buttocks is only red in the female, and that the face also 

 is pale red in the female but not in the male. We have seen 

 that this species is one of those mentioned by Von Fischer as 

 performing the gesture above discussed, and we may surmise 

 that in this case the habit is confined to the female, or at 

 least more strongly developed in the female sex. 



At the Zoological Gardens in London, on February 10, 1897, 

 I had an opportunity of personally observing the performance 

 of these gestures, and had some conversation on the subject 

 with one of the keepers, an experienced and intelligent man. 

 In one cage were two young Chacma baboons, less than half 

 grown. This species is not mentioned by either Darwin or 

 Fischer among those which have the buttocks coloured, or 



