The dependence of the menarche upon climatic influences is clearly shown by the statistical data collected from various regions of the world. We append the general compilation of _Gebhard_ dealing with this question.
For Europe the data furnished by _Ploss_ are grouped by _Gebhard_ in the following manner.
The average age at which menstruation first appears, according to the older statistics, is in Swedish Lapland 18, in Norway, 16.12. In Copenhagen it is 16.75, in St. Petersburg 14.5.
More recent statistics for Finland are furnished by _Engström_. Among 3,500 women of pure Finnish descent, he found that menstruation began:
8 years in 2 instances. 9 years in 2 instances. 10 years in 4 instances. 11 years in 41 instances. 12 years in 178 instances. 13 years in 458 instances. 14 years in 715 instances. 15 years in 778 instances. 16 years in 614 instances. 17 years in 369 instances. 18 years in 195 instances. 19 years in 91 instances. 20 years in 31 instances. 21 years in 8 instances. 22 years in 10 instances. 23 years in 2 instances. 24 years in 1 instance. 25 years in 0 instance. 26 years in 1 instance.
Thus, in nearly half of all Finnish women, menstruation begins with the completion of the fourteenth and fifteenth years. The statistics include women of all classes of society.
At the Pirogoff Congress _Grusdeff_ furnished particulars of the first onset of menstruation in Russia among 10,000 women. Menstruation began:
9 years in 1 instance. 10 years in 4 instances. 11 years in 31 instances. 12 years in 244 instances. 13 years in 864 instances. 14 years in 1641 instances. 15 years in 1795 instances. 16 years in 2012 instances. 17 years in 1692 instances. 18 years in 910 instances. 19 years in 498 instances. 20 years in 183 instances. 21 years in 65 instances. 22 years in 19 instances. 23 years in 5 instances. 24 years in 3 instances. 32 years in 1 instance.
In women of German race living in Russia puberty was earliest, occurring at the average age of 15.16 years; in Finnish women it was latest, occurring at the average age of 16.17 years.
In Germany, according to the tables of _Krieger_ and _L. Mayer_, who have recorded 11,500 cases in all, menstruation begins most commonly (in 18.931 per cent. of the cases) at the age of 15; the next most frequent age is 14 (18.213 per cent. of the cases).