is a maximum of births in February, and, consequently, of conceptions in May, and a minimum of births about July, with consequent minimum of conceptions in October.  Quetelet considered that the spring maximum of conceptions corresponded to an increase of vitality after the winter cold.  He pointed out that this sexual climax was better marked in the country than in towns, and accounted for this by the consideration that in the country the winter cold is more keenly felt.  Later, Wappaeus investigated the matter in various parts of northern and southern Europe as well as in Chile, and found that there was a maximum of conceptions in May and June attributable to season, and in Catholic countries strengthened by customs connected with ecclesiastical seasons.  This maximum was, he found, followed by a minimum in September, October, and November, due to gradually increasing exhaustion, and the influence of epidemic diseases, as well as the strain of harvest-work.  The minimum is reached in the south earlier than in the north.  About November conceptions again become more frequent, and reach the second maximum at about Christmas and New Year.  This second maximum is very slightly marked in southern countries, but strongly marked in northern countries (in Sweden the absolute maximum of conceptions is reached in December), and is due, in the opinion of Wappaeus, solely to social causes.  Villerme reached somewhat similar results.  Founding his study on 17,000,000 births, he showed that in France it was in April, May, and June, or from the spring equinox to the summer solstice, and nearer to the solstice than the equinox, that the maximum of fecundations takes place; while the minimum of births is normally in July, but is retarded by a wet and cold summer in such a manner that in August there are scarcely more births than in July, and, on the other hand, a very hot summer, accelerating the minimum of births, causes it to fall in June instead of in July.[152] He also showed that in Buenos Ayres, where the seasons are reversed, the conception-rate follows the reversed seasons, and is also raised by epochs of repose, of plentiful food, and of increased social life.  Sormani studied the periodicity of conception in Italy, and found that the spring maximum in the southern provinces occurs in May, and gradually falls later as one proceeds northward, until, in the extreme north of the peninsula, it occurs in July.  In southern Italy there is only one maximum and one minimum; in the north there are two.  The minimum which follows the spring or summer maximum increases as we approach the south, while the minimum associated with the winter cold increases as we approach the north.[153] Beukemann, who studied the matter in various parts of Germany, found that seasonal influence was specially marked in the case of illegitimate births.  The maximum of conceptions of illegitimate children takes place in the spring and summer of Europe generally; in Russia it takes place in the autumn and winter,