<< Penis and Clitoris >>

In the female and male mammal the external reproductive organs (Figures 118f-119f), the genitalia, develop embryologically from a common pattern. They are, therefore, homologous structures in the technical meaning of the term. In spite of considerable dissimilarities in the gross anatomy of the adult female and male genitalia, each structure in the one sex is homologous to some structure in the other sex. During the first two months of human embryonic development, the differences between the male and the female structures are so slight that it is very difficult to identify the sex of the embryo. In any consideration of the functions of the adult genitalia, and especially of their liability to sensory stimulation, it is important and imperative that one take into account the homologous origins of the structures in the two sexes.
For the embryology of the genitalia, see, for instance: Arey 1946:283-308. Patten 1946:575-607. Hamilton, Boyd, and Mossman 1947:193-223.

The embryonic phallus becomes the penis of the male or the clitoris of the female (Figures 118f-119f). The adult structures in both cases are richly supplied with nerves which terminate in what seem to be specialized sorts of end organs of touch—some of which are called Meissner’s corpuscles, and some Krause’s genital corpuscles.
Recent authors are inclined to discard the concept of Krause's corpuscles as end organs of touch and emphasize other end organs, especially Meissner's. See: Fulton 1949:3-6, 17. Ruch in Howell (Fulton edit.) 1949:304-306. Houssay et al. 1951:836. Blake and Ramsey 1951:29. For data on Krause’s corpuscles, see: Eberth 1904:249. Jordan 1934:147, 149, 438, 467. Wharton 1947:10. Bailey 1948:585, 630. Dickinson 1949:58. Fulton 1949:6. Maximow and Bloom 1952:181,524.

It is commonly understood that the lower edge of the head (the glans) of the penis, or what is technically known as the corona of the glans, is the area that is most sensitive to tactile stimulation. The area on the under surface of the penis directly below the cleft of the glans is similarly sensitive to stimulation. This latter area lies directly beneath the longitudinal fold (the frenum) by which the loose foreskin is attached if it has not been removed by circumcision.

It appears, however, that there is a minimum of sensation in the main shaft of the penis or in the skin covering it. When the frenum is moved to one side or cut away, pressure on the original point shows that it is as sensitive as it was before the removal of the skin. Stimulation applied by inserting a probe into the urethra similarly shows that the sensory nerves are not located between the urethra and the under surface of the organ, but between the urethra and the spongy mass which forms the shaft of the penis. It remains for the neurologist and the student of male anatomy to identify the exact nerves which are involved, but the present evidence seems to show that they end deep in the shaft of the penis and not in its epidermal covering.

In addition to reactions to sensory stimulation, mechanical reactions also appear to be involved in the erection of the penis. It has been generally assumed that the increased flow of blood into the organ during sexual arousal depends entirely upon circulatory changes which are effected by tactile or other sorts of erotic stimulation; but the possibility that mechanical effects may have something to do with the erection needs consideration. Forward pressures exerted on the corona of the glans not only effect sensory stimulation but, just as in stripping a wet piece of sponge rubber, also help crowd blood into the glans. Similarly, downward pressures on the upper (the distal) ends of the two spongy bodies ( the corpora cavernosa ) which constitute the shaft of the penis, and especially pressures on the upper edges of the spongy bodies at the point where they meet directly under the frenum, may stimulate the deep-seated nerves; but they may also have some mechanical effect in crowding blood into the corpora.

The effects of any direct stimulation of the penis are so obvious that the organ has assumed a significance which probably exceeds its real importance. The male is likely to localize most of his sexual reactions in his genitalia, and his sexual partner is also likely to consider that this is the part of the body which must be stimulated if the male is to be aroused. This overemphasis on genital action has served, more than anything else, to divert attention from the activities which go on in other parts of the body during sexual response. It has even been suggested that the larger size of the male phallus accounts for most of the differences between female and male sexual responses, and that a female who had a phallus as large as the average penis might respond as quickly, as frequently, and as intensely as the average male. But this is not in accord with our understanding of the basic factors in sexual response. There are fundamental psychologic differences between the two sexes which could not be affected by any genital transformation. This opinion is further confirmed by the fact that among several of the other primates, including the gibbon and some of the monkeys, the clitoris of the female is about as large as the penis of the male, but the basic psychosexual differences between the female and male are still present.
For data on the large clitoris of some primates, see: Hooton 1942:175, 231, 252, 273. Ford and Beach 1951:21. In examining spider monkeys we find the clitoris may be as long as or longer than the penis, although not as large in diameter.

Clitoris
The clitoris (Figure 118f), which is the phallus of the female, is the homologue of the penis of the male. The shaft of the clitoris may average something over an inch in length. It has a diameter which is less than that of a pencil. Most of the clitoris is embedded in the soft tissue which constitutes the upper (i.e., the anterior) wall of the vestibule to the vagina. The head (glans) of the clitoris is ordinarily the only portion which protrudes beyond the body. In many females the foreskin (the hood) of the clitoris completely covers the head and adheres to it, and then no portion of the clitoris is readily apparent. Because of the small size of any protrudent portions, no localizations of sensitive areas on the corona or on other parts of the clitoris have been recorded.

Also because of its small size and the limited protrusion of the clitoris, many males do not understand that it may be as important a center of stimulation for females as the penis is for males. However, most females consciously or subconsciously recognize the importance of this structure in sexual response. There are many females who are incapable of maximum arousal unless the clitoris is sufficiently stimulated.

In connection with the present study, five gynecologists have cooperated by testing the sensitivity of the clitoris and other parts of the genitalia of nearly nine hundred females. The results, shown in Table 174, constitute a precise and important body of data on a matter which has heretofore been poorly understood and vigorously debated. The record shows that there is some individual variation in the sensitivity of the clitoris: 2 per cent of the tested women seemed to be unaware of tactile stimulation, but 98 per cent were aware of such tactile stimulation of the organ. Similarly, there is considerable evidence that most females respond erotically, often with considerable intensity and immediacy, whenever the clitoris is tactilely stimulated.

We have already noted that a high percentage of all the females who masturbate use techniques which involve some sort of rhythmic stimulation of the clitoris, usually with a finger or several fingers or the whole hand. Such techniques often involve the stimulation of the inner surfaces of the labia minora as well, but then each digital stroke usually ends against the clitoris. When the technique includes rhythmic pressure on those structures, the effectiveness of the action may still depend upon the sensitivity of the clitoris and of the labia minora. Even direct penetrations of the vagina during masturbation may depend for their effectiveness on the fact that the base of the clitoris, which is located in the anterior wall of the vagina, may be stimulated by the penetrating object.

Whenever female homosexual relations include genital techniques, the clitoris is usually involved. This is particularly significant because the partners in such contacts often know more about female genital function than either of the partners in a heterosexual relation. While there are more females than males who achieve orgasm through the stimulation of some area other than their genitalia, certainly there are no structures in the female which are more sensitive than the clitoris, the labia minora, and the extension of the labia into the vestibule of the vagina.

The male who comprehends the importance of the clitoris regularly provides manual or other mechanical stimulation of that structure during pre-coital petting. In coitus, he sees to it that the clitoris makes contact with his pubic area, the base of his penis, or some other part of his body. Oral stimulation of the female genitalia is most often directed toward the labia minora or the clitoris.

Some of the psychoanalysts, ignoring the anatomic data, minimize the importance of the clitoris while insisting on the importance of the vagina in female sexual response.

Urethra and Meatus
The penis of the male is normally penetrated for its full length by the urethra (Figure 119f). The urethra of the female (Figure 118f) does not penetrate the clitoris; instead it lies in the soft tissues which constitute the upper (the anterior) wall of the vagina. The opening of the urethra of the male (the meatus) is normally on the tip of the head of the penis; in the female it is located between the clitoris and the entrance to the vagina.

A few persons, females and males, employ masturbatory techniques which include insertions of objects into the urethra. The urethral lining which has not become accustomed to such penetration is so sensitive that most individuals, upon initial experimentation, desist from further activity. More experienced persons claim that they receive some erotic stimulation from the penetrations. The recorded satisfactions may include reactions to pain, and sometimes they may be wholly psychologic in origin. Urethral insertions may also stimulate the nerves which lie in the tissue about the urethra of the female, or deep in the shaft of the penis of the male.
Urethral insertions are also noted, for instance, in: Bloch 1908:411. Havelock Ellis 1936(1,1):171-173. Dickinson 1949:63, 69. Grafenberg 1950:146. Haire 1951:147.

There is evidence that the area surrounding the meatus is supplied in some individuals with an accumulation of nerves. Consequently, direct stimulation of the meatus is sometimes included in the masturbatory procedures. This may happen more often in the female than in the male.
For nerve endings located about the urethral meatus of the female, see, for instance: Lewis 1942:8. Dickinson 1949:62.

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