Since Griffin has to walk around naked to be truly invisible, he is at the mercy of the weather. Although the weather gets warmer as time passes in the book, Griffin’s stays in London and Iping are both particularly chilly, so he is afflicted with a cold.
He frequently sneezes, often at inopportune moments when he is trying to remain undetected or appear powerful. For example, in Chapter 9, when Griffin seeks out Mr. Marvel to help him, Griffin sneezes while he is trying to present himself as a “man of power”:
“I’ve chosen you,” said the Voice. “You are the only man except some of those fools down there, who knows there is such a thing as an invisible man. You have to be my helper. Help me—and I will do great things for you. An invisible man is a man of power.” He stopped for a moment to sneeze violently.
The sneezing demonstrates that although Griffin has power, he is still mortal. He still suffers the travails of the flesh and is not immune to sickness. He has transcended the natural order in some respects but is still subject to the confines of a physical body in others.
The contrast is also meant to be humorous. Griffin poses himself as someone big and strong, making threats and promises that demonstrate power, but he has to stop to sneeze, which is somewhat silly. Other times he tries to fully exert his powers of invisibility, like when he tries to wander around Mrs. Hall's Inn discretely or rob the shopkeeper's house, sneezing similarly acts as an obstacle, alerting or almost alerting an outside observer to his presence.
Antagonistic dogs—or, rather, dogs that antagonize Griffin—appear throughout The Invisible Man. He is somewhat protected from other humans by his invisibility, but because of dogs' heightened sense of smell, he is unable to escape their perception. This motif is particularly apparent in Chapter 21, when Griffin says in his confession to Doctor Kemp:
I had never realised it before, but the nose is to the mind of a dog what the eye is to the mind of a seeing man. Dogs perceive the scent of a man moving as men perceive his vision.
After he was barked at by dogs in London, Griffin develops a fear of them. They are his natural antagonists and one of his biggest weaknesses. Since dogs are his main weakness, they are what Doctor Kemp uses to bring Griffin to his eventual downfall. In Port Burdock, when Doctor Kemp and Mr. Adye devise a plan to apprehend Griffin, Doctor Kemp emphasizes that there should be many dogs present. Doctor Kemp is right to do so, for the dogs of Port Burdock make the night difficult for Griffin because they nullify his powers of invisibility.
At the end of the novel when Griffin dies at the hands of Mr. Kemp and the mob, the narrative uses a simile to compare Mr. Kemp to a dog:
Kemp clung to him in front like a hound to a stag, and a dozen hands gripped, clutched, and tore at the Unseen.
Doctor Kemp, in attacking the invisible man, is doglike. The choice to compare Kemp to a hound demonstrates that Kemp is Griffin’s downfall, for Griffin’s confession to Doctor Kemp is what seals his death. Without said confession, in which the weakness of dogs and Griffin's grand plans are revealed, Griffin would have been able to go around terrorizing people indefinitely.
Griffin is literally invisible, so the novel explores the physical implications of invisibility, but the novel also explores the social problem of being invisible—in other words, the effects of being an outcast in society. The main advantage of physical invisibility is impunity. That is, being invisible means no one can pin responsibility on you. Since no one can see the Invisible Man's face, he can commit most crimes without being identified.
What's more, as Griffin points out, invisibility is particularly useful for the crime of murder. It is difficult to defend against a punch or kick that one can't see coming, so self-defense against the Invisible Man is difficult. However, invisibility has a major downside: it makes life difficult to enjoy. In Chapter 23, after Griffin explains how he had to steal to survive, he tells Mr. Kemp about one of the disadvantages of being invisible:
Before I made this mad experiment I had dreamt of a thousand advantages. That afternoon it seemed all disappointment. I went over the heads of the things a man reckons desirable. No doubt invisibility made it possible to get them, but it made it impossible to enjoy them when they are got.
By gaining impunity, Griffin sacrificed pleasure. By foregoing responsibility, he sacrificed being able to enjoy rewards. He can not eat in public, has no ability to socialize, nor to gain recognition or societal power in the least. As an invisible man, he is on his own.
However, even before his transformation into actual invisibility, there is a sense in which he is metaphorically invisible. He lived alone, doing his research in poverty. As someone with albinism, he already was made an outcast by an unfair society. No one truly saw him—they did not recognize him for his achievements or strive to reach out to him in human companionship.
Antagonistic dogs—or, rather, dogs that antagonize Griffin—appear throughout The Invisible Man. He is somewhat protected from other humans by his invisibility, but because of dogs' heightened sense of smell, he is unable to escape their perception. This motif is particularly apparent in Chapter 21, when Griffin says in his confession to Doctor Kemp:
I had never realised it before, but the nose is to the mind of a dog what the eye is to the mind of a seeing man. Dogs perceive the scent of a man moving as men perceive his vision.
After he was barked at by dogs in London, Griffin develops a fear of them. They are his natural antagonists and one of his biggest weaknesses. Since dogs are his main weakness, they are what Doctor Kemp uses to bring Griffin to his eventual downfall. In Port Burdock, when Doctor Kemp and Mr. Adye devise a plan to apprehend Griffin, Doctor Kemp emphasizes that there should be many dogs present. Doctor Kemp is right to do so, for the dogs of Port Burdock make the night difficult for Griffin because they nullify his powers of invisibility.
At the end of the novel when Griffin dies at the hands of Mr. Kemp and the mob, the narrative uses a simile to compare Mr. Kemp to a dog:
Kemp clung to him in front like a hound to a stag, and a dozen hands gripped, clutched, and tore at the Unseen.
Doctor Kemp, in attacking the invisible man, is doglike. The choice to compare Kemp to a hound demonstrates that Kemp is Griffin’s downfall, for Griffin’s confession to Doctor Kemp is what seals his death. Without said confession, in which the weakness of dogs and Griffin's grand plans are revealed, Griffin would have been able to go around terrorizing people indefinitely.
