about puberty and dies out slowly during adolescence. While fairly common in young women, it is usually much less severe, but tends to be exacerbated at the menstrual periods; it is also apt to appear at the change of life. (Stephen Mackenzie, "The Etiology and Treatment of Acne Vulgaris," British Medical Journal, September 29, 1894. Laycock [Nervous Diseases of Women, 1840, p. 23] pointed out that acne occurs chiefly in those parts of the surface covered by sexual hair. A lucid account of the origin of acne will be found in Woods Hutchinson's Studies in Human and Comparative Pathology, pp. 179-184. G. J. Engelmann ["The Hystero-neuroses," Gynæcological Transactions, 1887, pp. 124 et seq.] discusses various pathological disorders of the skin as reflex disturbances originating in the sexual sphere.)

The influence of menstruation in exacerbating acne has been called in question, but it seems to be well established. Thus, Bulkley ("Relation between Certain Diseases of the Skin and the Menstrual Function," Transactions of the Medical Society of New York, 1901, p. 328) found that, in 510 cases of acne in women, 145, or nearly one-third, were worse about the monthly period. Sometimes it only appeared during menstruation. The exacerbation occurred much more frequently just before than just after the period. There was usually some disturbance of menstruation. Various other disorders of the skin show a similar relationship to menstruation.

It has been asserted that masturbation is a frequent or constant cause of acne at puberty. (See, e.g., discussion in British Medical Journal, July, 1882.) This cannot be accepted. Acne very frequently occurs without masturbation, and masturbation is very frequently practiced without producing acne. At the same time we may well believe that at the period of puberty, when the pilo-sebaceous system is already in sensitive touch with the sexual system, the shock of frequently repeated masturbation may (in the same way as disordered menstruation) have its repercussion on the skin. Thus, a lady has informed me that at about the age of 18 she found that frequently repeated masturbation was followed by the appearance of comedones.

[2]

[3]

[4]

II.

Touch, as has already been remarked, is the least intellectual of the senses. There is, however, one form of touch sensation—that is to say, ticklishness—which is of so special and peculiar a nature that it has sometimes been put aside in a class apart from all other touch sensations. Scaliger proposed to class titillation as a sixth, or separate, sense. Alrutz, of Upsala, regards tickling as a milder degree of itching, and considers that the two together constitute a sensation of distinct quality with distinct end-organs, for the mediation of that quality.^[5] However we may regard this extreme view, tickling is certainly a specialized modification of touch and it is at the same time the most intellectual mode of touch sensation and that with the closest connection with the sexual sphere. To regard tickling as an intellectual manifestation may cause surprise, more especially when it is remembered that ticklishness is a form of sensation which reaches full development very early in life, and it has to be admitted that, as compared even with the messages that may be sent through smell and taste, the intellectual element in ticklishness remains small. But its presence here has been independently recognized by various investigators. Groos points out the psychic factor in tickling as evidenced by the impossibility of self-tickling.^[6] Louis Robinson considers that ticklishness "appears to be one of the simplest developments of mechanical and automatic nervous processes in the direction of the complex functioning of the higher centres which comes within the scope of psychology,"^[7] Stanley Hall and Allin remark that "these minimal touch excitations represent the very oldest stratum of psychic life in the soul."^[8] Hirman Stanley, in a somewhat similar manner, pushes the intellectual element in ticklishness very far back and associates it with "tentacular experience." "By temporary self-extension," he remarks, "even low amœboid organisms have slight, but suggestive, touch experiences that stimulate very general and violent reactions, and in higher organisms extended touch-organs, as tentacles, antennæ, hair, etc., become permanent and very delicately sensitive organs, where minimal contacts have very distinct and powerful reactions." Thus ticklishness would be the survival of long passed ancestral tentacular experience, which, originally a stimulation producing intense agitation and alarm, has now become merely a play activity and a source of keen pleasure.^[9]

We need not, however, go so far back in the zoölogical series to explain the origin and significance of tickling in the human species. Sir J. Y. Simpson suggested, in an elaborate study of the position of the child in the womb, that the extreme excitomotory sensibility of the skin in various regions, such as the sole of the foot, the knee, the sides, which already exists before birth, has for its object the excitation and preservation of the muscular movements necessary to keep the fœtus in the most favorable position in the womb.^[10] It is, in fact, certainly the case that the stimulation of all the ticklish regions in the body tends to produce exactly that curled up position of extreme muscular flexion and general ovoid shape which is the normal position of the fœtus in the womb. We may well believe that in this early developed reflex activity we have the basis of that somewhat more