Themes in The Metamorphosis
Note the irony of these words: Gregor's father, still in his human body, begins to act even more like an animal than Gregor, hissing at his son and forcing him back into his little room. Gregor has (quite admirably) attempted to act just like a human and to get up, head to work, catch the train, and even walk as if nothing had happened. This line proves that humans can nevertheless still be inhumane.
Kafka separates the mind and the body here, suggesting that they're both entities that can be "fled" or get left behind, and that when this happens the body and the mind act of their own accord. In this case, the narrator's jaw snaps in shock and horror, as if he's trying to speak. In Gregor's case, his body and his mind are at a disconnect, but have grown gradually more aligned as he loses his ability to speak and learns how to walk.
Existentialists believe that their experiences and ideas isolate them in many ways from other people, making communication very difficult. It becomes clear in this passage that this existentialist belief has in fact become a reality, and that Gregor is no longer able to speak German (the original language of The Metamorphosis). His parents begin to speak through his room, effectively rendering him and it insignificant, almost as if they don't exist.
The absurdity of this situation has led Gregor to ask some existential questions about the nature of reality and human experience: if he, an otherwise unremarkable man, could suddenly and without warning change into this pest, then surely it must be possible that others have done so in the past. In thinking this, Gregor attempts to relate to the attorney and, by extension, to all of humanity. This attempt is ultimately unsuccessful.
There's a certain arrogance in these thoughts, which, when read in a certain light, seem to suggest that Gregor alone is being persecuted, and that no one else suffers but him. He does, of course, work with a number of other people at the firm, all of whom are being persecuted at least as much as him. Kafka's characters often have this experience of being controlled by and vaguely afraid of an absurd, overly-officious bureaucracy, and indeed this is one of his major themes.
Instead of trying to reverse his metamorphosis, he passively waits for it to resolve itself, assuming that he'll revert back to his former self if he just waits. He doesn't realize that this inability to decide is in fact in keeping with his personality, and that if continues to behave this way he'll never turn back. This element of existentialism—that there's no common single experience of being human and that each person must create his or her own reality—is crucial to understanding Gregor Samsa's acceptance of his situation.
Notice that the lady's fur muff makes her look almost like an animal. This image parallels Gregor's own transformation, into which his body or human self has disappeared, like the lady's forearm. In aligning the transformed Gregor with the woman in the boa, Kafka suggests that Gregor's real problem may be related to his sexuality, in particular, his inability to meet women.
Notice how Kafka subtly implies that, because Gregor is no longer a human being, he no longer belongs in this room. This establishes the theme of not belonging or being out of place, which defines Gregor's experience both before and after his transformation.
From Gregor's perspective, his mother and father seem to merge into a single, multi-limbed creature, monstrous in its intention to both hurt Gregor and spare his life. With this image, we can clearly see that the humans in this story are the real threats and that Gregor, who seems to be physically incapable of murder, is at the mercy of these strange, cruel figures.
In spite of his condition, Gregor has learned through his interactions with Grete how to communicate with his family, using body language and physical cues instead of real speech. This act of pushing on the door reminds one of a dog seeking to be let in. That his family hasn't bothered to interpret his body language, and that they assume him to be deaf and dumb, further illustrates the fact that they never fully understood him.
Note that this if the first time Gregor has been out of his room since Part I, when he opened the door to speak with the attorney. In that time, his room has been characterized as a place of infirmity and of gradual decline, in which Gregor slowly loses his self-succiency and becomes dependent on others. That the mother has collapsed in his room suggests that she, too, has become dependent on others, as evidenced by the fact that she doesn't work and has trouble breathing.
Kafka doesn't dwell on the point, and Gregor doesn't seem to think of it at all, but this act of covering up the picture with his body has overt sexual overtones (in that Gregor presses it against a part of his body that is, in essence, nude). This is the only direct display of sexuality in the book, and in the end it proves to be an act of futility, because Gregor can no longer act on his desires, but can only preserve the memory that he once had them.
This may well be the first time we've seen Gregor angry. He's been at various times confused, grateful, considerate, and suspicious, but the vehemence with which he protects this picture is unprecedented and a little frightening. It's at once an incredibly human thing to do (covet that which we desire as our own) and a display of inhuman intensity, in which Gregor thinks about attacking his own sister.
Notice the reversal of roles here: Gregor's sister, the daughter, holds her mother's hand, acting as if she's the child in their relationship and as if she must protect her mother from what she's able to witness. It's worth noting that a similar reversal of roles happened with the father when Gregor become the provider of the family. Kafka draws this parallel to suggest that the old generation, unlike the new, isn't as prepared to handle unexpected events as their younger counterparts.
This is the seventh time that the word "door" (German: Tür) has been used in this short paragraph. This repetition makes the door a symbol of Gregor's inability to interact and communicate with the rest of his family and, by extension, all of humanity. This builds on the theme of isolation prevalent in the book.
His sister once again proves to be Gregor's only ally and has sweetly prepared this milk for him, knowing that he'll be hungry and trying to show him some consideration. However, the placement of the milk (in a bowl on the floor) and the presence of the chunks of bread (as if he were a dog) further emphasize that he's not human. He's being treated here almost like an unwanted pet.
Here, "young body" can be understood as a new or newly matured body, indicating that Grete has grown up and come into her own as a woman. Over the course of this short novel, Grete has undergone a transformation of her own, albeit a natural one, that sees her go from the sad, weeping girl of Part I to the vibrant, beautiful young woman of Part III. Her metamorphosis serves as a counterpoint to Gregor's, reminding the reader that drastic changes like his aren't uncommon, but that they tend to happen slowly, imperceptibly, almost as if they weren't happening at all.
In Part II, Kafka used the image of Gregor being "nailed down" by the apple his father threw at him to allude to Christ's crucifixion. Here, he alludes to the hour of Christ's death (three o'clock) to further equate Gregor with the martyr and to suggest that he's sacrificing himself in order so that his family might have a better life.
Many things have fallen in the course of this novel: the violin, the spilt coffee, the mother when she tripped over her skirts, the attorney who had to catch himself on the stairs, and Gregor himself, falling from the ceiling. This act of falling is akin to forgetting one's self, as when the mother allows the violin to fall from her lap, which Grete has placed there carelessly, as if forgetting how beautiful her music is. Indeed, it's as if Grete has forgotten herself entirely.
Kafka asks the central question of the novel: what does it mean to be human, and does Gregor's transformation ever really strip him of his humanity? It's true that many animals, including bugs, are capable of creating and understanding their own kinds of music (birds, crickets, and whales being the prime examples), but it's rare for an animal to understand and appreciate human music. Ultimately, Kafka doesn't answer this question using music, and the reader has to figure it out for themselves.