Transplantation of the ureters has been one of the most perplexing problems that have ever engaged the attention of surgeons. The reason is that heretofore this operation has been considered to be nothing more than the artisan's technic of performing a mechanical feat. Instead, it must be looked on as nothing less than the means of execution of a biologic plan for transmutation of the mammalian to the avian eliminative system. This involves the studious consideration of physics, anatomy, physiology and bacteriology, as well as mechanics, in formulating a technic. Our concrete problem is the transmission or transfer of the relatively sterile product of a vital secreting or excreting organ, in which the pressure must be low and regular, into a muscular reservoir, infested with bacteria, in which the pressure is high and irregular. Furthermore, the patient must be alive and well after the operation. PHYSICS As far as I