Three times in the last two months, researchers from St. Luke’s-Roosevelt Hospital Center in Manhattan headed across town to the Animal Medical Center to look at dogs.

Doctors at the hospital’s Vascular Birthmark Institute were enticed by the chance to study anomalies of the arteries and veins that are rare in humans but common in dogs. And the traffic between human and animal hospitals flows in the other direction, too: Late last month, veterinarians from the Animal Medical Center began meeting with their counterparts at Memorial Sloan-Kettering Cancer Center to set up trials of a noninvasive device for removing tumors of the urinary tract with electrical impulses.

Exchanges of this sort are becoming increasingly common. Once a narrow trail traveled by a few hardy pioneers, the road connecting veterinary colleges and human medical institutions has become a busy thoroughfare over the last five years or so, with a steady flow of researchers representing a wide variety of medical disciplines on both sides.

One reason is a growing frustration with the inefficiency of using the rodent model in lab research, which often fails to translate to human subjects. So researchers are turning their attention to the naturally occurring diseases in dogs, horses, sheep and pigs, whose physiology and anatomy more closely resemble those of humans.