In this connection we may well bring into line a remarkable group of phenomena concerning which much evidence has now accumulated. I refer to the use of various appliances, fixed in or around the penis, whether permanently or temporarily during coitus, such appliance being employed at the woman's instigation and solely in order to heighten her excitement in congress. These appliances have their great center among the Indonesian peoples (in Borneo, Java, Sumatra, the Malay peninsula, the Philippines, etc.), thence extending in a modified form through China, to become, it appears, considerably prevalent in Russia; I have also a note of their appearance in India. They have another widely diffused center, through which, however, they are more sparsely scattered, among the American Indians of the northern and more especially of the southern continents. Amerigo Vespucci and other early travelers noted the existence of some of these appliances, and since Miklucho-Macleay carefully described them as used in Borneo[82] their existence has been generally recognized. They are usually regarded merely as ethnological curiosities. As such they would not concern us here. Their real significance for us is that they illustrate the comparative insensitiveness of the genital canal in women, while at the same time they show that a certain amount of what we cannot but regard as painful stimulation is craved by women, in order to heighten tumescence and increase sexual pleasure, even though it can only by procured by artificial methods. It is, of course, possible to argue that in these cases we are not concerned with pain at all, but with a strong stimulation that is felt as purely pleasurable. There can be no doubt, however, that in the absence of sexual excitement this stimulation would be felt as purely painful, and--in the light of our previous discussion--we may, perhaps, fairly regard it as a painful stimulation which is craved, not because it is itself pleasurable, but because it heightens the highly pleasurable state of tumescence.