ONE FIGURI
In addition to reduction in ear size, the short ear gene (autosomal recessive -se, Lynch, , 2 l ) in the house mouse, Mus ~nusculus, produces many other anatomical changes. Among these may be cited alteration in the shape of the skull, muscular waviness of the tail (Snell, ,31), reduction in the number of ribs (Snell, '35; Green and Green, '46), reduction in body size (Castle et al., '36; Law, '38), malformation of the xiphisternum (Green and McNutt, '41), changes in the relationships of abdominal nerves and blood vessels (Green, '50), hydrotic kidneys, reduction in the size of the vertebral column, skull and long bones and reduction in size or absence of many small bones or bony processes (Green, '51). Up to this time, all of the recorded effects of the gene have been anatomical. I n view of the marked pleiotropism of the short ear gene, the gene may be responsible for physiological effects which are not so readily detectable.
Since nothing is known of the process in development on which the short ear gene acts other than that it must be a process concerned with cartilage development (Green and Green, '42; Green, '51), the starting point for an investigation of the possible physiological effects of the gene must be arbitrary. Since the urine of animals contains the waste products of their metabolism, it furnishes a readily accessible source of information on their metabolic processes. If a difference in the metabolism of short ear and normal mice exists, it may