Figure 2. Routes of drug administration in frogs. Top, systemic administration into the dorsal lymph sac. Middle, spinal administration by direct percutaneous intraspinal injection (i.s.). Bottom, supraspinal administration by injector placed in the third ventricle of the brain (i.c.v.). See text for further details.

Craig W. Stevens, Ph.D. "A Whole-Animal Alternative Model for Pain Research" Animal Welfare Information Center Newsletter, 8(3):3-5, Winter 1997/1998.