"The Laboratory" is basically a single, uninterrupted speech delivered by one character in the poem to another. In a play, that's what you would call a monologue. Browning is famous for his poetic monologues. Other examples include "Porphyria's Lover" and "My Last Duchess." As it happens, both of these other monologue poems are also about love and murder. So if you're reading a disturbing, grisly poem, told from one person's point of view, chances are you're dealing with Robert Browning.