This section is from the book "The Dogs Of Great Britain, America, And Other Countries. Their Breeding, Training, and Management in Health and Disease", by John Henry Walsh (Stonehenge). Also available from Amazon: The Dogs Of Great Britain, America And Other Countries.
Puppies of all kinds vary in form so much between the weaning time and the period of full growth, that there is great difficulty in making a choice which shall be proved by subsequent events to be on reliable grounds. All young animals grow by fits and starts, the proportions varying with the stage of development in which any part is at the time of examination. Thus at the fourth month a puppy may look too long, but during the next month he may have grown so much in the legs that he no longer looks so. Again, another may be all legs and wings in the middle of his growth, but he may finally grow down to a strong, low, and muscular dog. So also with the fore and hind quarters, they may grow alternately, and one month the fore quarter may be low, and the next the hind. None but an experienced eye therefore can pretend to foresee, after the period of weaning, what will be the final shape; but either soon after that time, or a day or two after birth, a pretty good guess may be given, subject to the continuation of health, and to proper rearing in all respects. Bad feet can soon be detected, but the limbs grow into a good shape after most extraordinary deviations from the line of beauty, particularly in the greyhound, which is often apparently deformed in his joints when half grown.
The most unwieldy-looking animals often "fine" down into the best shapes, and should not be carelessly rejected without the fiat being pronounced by a breeder of experience.