It must be remarked that the increased tendency to premature birth, while in part it may be due to general tendencies of civilization, is also in part due to very definite and preventable causes. Syphilis, alcoholism, and attempts to produce abortion are among the not uncommon causes of premature birth (see, e.g., G.F. McCleary, "The Influence of Antenatal Conditions on Infantile Mortality," _British Medical Journal_, Aug. 13, 1904). Premature birth ought to be avoided, because the child born too early is insufficiently equipped for the task before him. Astengo, dealing with nearly 19,000 cases at the Lariboisière Hospital in Paris and the Maternité, found, that reckoning from the date of the last menstruation, there is a direct relation between the weight of the infant at birth and the length of the pregnancy. The longer the pregnancy, the finer the child (Astengo, _Rapport du Poids des Enfants à la Durée de la Grossesse_, Thèse de Paris, 1905). The frequency of premature birth is probably as great in England as in France. Ballantyne states (_Manual of Antenatal Pathology; The Foetus_, p. 456) that for practical purposes the frequency of premature labors in maternity hospitals may be put at 20 per cent., but that if all infants weighing less than 3,000 grammes are to be regarded as premature, it rises to 41.5 per cent. That premature birth is increasing in England seems to be indicated by the fact that during the past twenty-five years there has been a steady rise in the mortality rate from premature birth. McCleary, who discusses this point and considers the increase real, concludes that "it would appear that there has been a diminution in the quality as well as in the quantity of our output of babies" (see also a discussion, introduced by Dawson Williams, on "Physical Deterioration," _British Medical Journal_, Oct. 14, 1905). It need scarcely be pointed out that not only is immaturity a cause of deterioration in the infants that survive, but that it alone serves enormously to decrease the number of infants that are able to survive. Thus G. Newman states (loc. cit.) that in most large English urban districts immaturity is the chief cause of infant mortality, furnishing about 30 per cent. of the infant deaths; even in London (Islington) Alfred Harris (_British Medical Journal_, Dec. 14, 1907) finds that it is responsible for nearly 17 per cent. of the infantile deaths. It is estimated by Newman that about half of the mothers of infants dying of immaturity suffer from marked ill-health and poor physique; they are not, therefore, fitted to be mothers.