Why did the film version of Frankenstein create the character Fritz?

One interesting aspect in which the novel Frankenstein differed significantly from the movie was the absence of the character of Fritz in the scenes where Dr. Frankenstein collected and animated the body of the monster. This glaring difference makes me wonder what the creators of the film version sought to add to those scenes by the addition of Frankenstein’s humpbacked assistant.

The image of Fritz certainly draws upon the mutual fear shared by most humans of the deformed and mentally unstable. His physical weakness and abnormalities add to the creepy feeling of the film. However I think that it is Fritz’s mental abnormalities that really frighten the viewer, rather than his physical ones. Fritz is completely obedient to Frankenstein’s commands without any boundaries that are usually imbued upon man by our shared mores — intercultural laws governing behavior. Combine this with his mad demeanor, and you have the perfect character to enable Dr. Frankenstein to complete his dark quest.

Along with Fritz’s mental and physical abnormalities, his cruelty and pleasure in causing pain make him a frightening character. Once the monster is animated, Fritz tortures him with both fire and whips. He clearly enjoys his newfound power over the “lesser being”, but in the end is killed by the target of his cruelty.

While the film relies partially on the imagery of Fritz to inspire horror, the novel relies more on the unwavering obsession of Dr. Frankenstein. I think that this is partially due to the difference in the medium. Horror in the form of written word has the advantage of forcing the reader to really think and ponder the words and actions of the characters, whereas horror in the form of film has the advantage that it visually engages the viewer. Is it possible that Fritz is the physical, visual embodiment of Dr. Frankenstein’s obsession? The written version had the luxury of slowly taking us step by step though Frankenstein’s experiment, leaving us more incredulous at the lengths to which his obsession would drive him with each passing atrocity — from stealing body parts from graves to taking surgical instruments from slaughter houses. Maybe the film version attempts to express that same level of freighting obsession through the creation of the character of Fritz.