The age and condition of the sow should also be considered. A young sow of about twelve months should not have more than seven or eight pigs left on her to rear, whereas with her succeeding litters until she is at least four years old she would rear at least ten pigs each litter. After the sow has reached the age of about four years, if that time has been fully employed in her maternal duties, she becomes gradually less able to rear so large a number of pigs with an equal amount of success. It is then advisable to vary the number according to the season, and to the physical condition of the sow; generally speaking an aged sow will bring up more pigs in the summer months than in the colder months. Reference is made elsewhere to the manner in which the young pigs should be cared for until they are weaned from their dam, but no harm can arise from a repetition of the advice that the young pigs should be so managed and fed that only the very slightest difference will be noticed by the youngsters when parted from their mother. Many pigs are permanently checked in growth by being suddenly deprived of a full supply of mother's milk if weaned when their digestive organs are insufficiently developed as to treat a sufficiency of food to make growth and progress without the assistance received from their mother's milk. Opinions differ as to the age at which little pigs are sufficiently developed as to exist and thrive without their dam's help. Here again the time of the year, not only as far as the weather is concerned, but the desirability of prompt or deferred remating of the sow in order that her succeeding litters should arrive during the most favourable portions of the year, must be considered. The thrift and growth of each litter of pigs varies greatly. The health of the sow, her condition before farrowing, and other causes, some of which are not always on the surface, have their influence, but it may be taken as a rule that young pigs are fully able to fend for themselves by the time they are eight weeks old. Should it be possible to allow the pigs to remain on the sow for so long a time as twelve weeks without prejudicing the next litters as to the time of year of their arrival, the pigs may benefit, and no loss of food will be sustained, since it has been clearly proved that pigs beyond the age of eight weeks can be fed quite as economically, if not more so, on the sow than if weaned. It may also be possible to feed the sow on somewhat coarser and less expensive food than could be satisfactorily fed to the young pigs, as her digestive organs would be better able to treat the coarser food. Another advantage generally follows keeping the pigs for a longer time on the sow if the latter be well fed is that she will be in a stronger and better condition to start the building up of her next litter.