Nationality. Age in years of males. Age in years of females. English 25.94 24.69 French 28.41 25.32 Norwegians 28.51 26.98 Dutch 29.15 27.78 Belgians 29.94 28.19 These figures show clearly what a gap there is between the coming of sexual maturity and the age at which marriage can be undertaken. The decay of the reproductive functions shows a series of disharmonies similar to those that occur during development. Spermatozoa continue to be formed throughout the greater part of the life of a man, and may still be found even in very old men. Pawloff, for instance, discovered that they were present in abundance in the case of a man at the age of ninety-four, and this observation is not unique.[117] But the presence of ripe spermatozoa is not the only condition necessary for functional virility. In the case of old men it happens frequently that there is incapacity to make normal use of the spermatozoa that are produced. This brings about a series of discomforts in the sexual functions of advanced life which, however, do not prevent the retention of the specific sensation and desire until a very extreme old age. Doctors, in hospitals devoted to old men, have noticed to what an extent their patients are engrossed by sexuality. Even some of the ancient authors have noticed how the amorous sentiments of old men turn into a perverted attraction to youths. Sexual irritability and amorousness not only appear before sexual maturity and general fitness of the organism for marriage, but they remain after the disappearance of these. It is remarkable to notice how profound is the difference between the disharmonies of the reproductive functions in man and the perfect condition of adaptation of the same functions in the higher plants. In the case of the higher plants, as I described in my second chapter, the arrangements are complicated on account of the necessary mediation of insect life. Notwithstanding this, the perfection of the adaptation is remarkable. At the exact time when the reproductive products are ripe, the petals open and the nectar is secreted, while, in addition, at this time many flowers discharge odours agreeable to insects. Attracted by the scents and colours, the insects visit the flowers in quest of pollen or nectar, and, becoming dusted with pollen, carry it to the stigmas of the next flowers they visit. As soon as fertilisation has taken place the petals fade, the scents are no longer produced, and the insects cease to visit the flowers to which they are no longer necessary.