You can withstand one bite from a rattlesnake and/or scorpion, but not two. If he gets bitten once, red daggers appear around the edges of the screen.
Pay close attention to arrows while in the Mine Cart they instruct you to switch tracks by swiping left or right.
Keep in mind that you need diamonds to activate checkpoints, and Macaw Tokens to start from checkpoints. You must head to the Store, then the Checkpoints section.
Macaw Token x 10 (6,000 treasure pieces or 10 diamonds): Macaw Tokens allow Harry to start running from Checkpoints you have activated.
Life Tonic x10 (4,000 treasure pieces of 10 diamonds): Life Tonics last a short amount of time, and will immediately revive Harry if he dies.
Haste Tonic x10 (1,600 treasure pieces or six diamonds): Drinking a Haste Tonic will boost Harry's running speed for a short amount of time.
Anti-Venom Tonic x10 (3,000 treasure pieces, eight diamonds): Anti-Venom Tonics will instantly cure Harry of the ill effects of any bites and stings.
Jaguar Token (1,200 treasure pieces, four diamonds): Increase the time that each Jaguar carries Harry.
Life Tonic (2,800 treasure pieces, eight diamonds): Life Tonics will protect Harry for longer.
Haste Tonic (1,200 treasure pieces, four diamonds): Increase the duration of Haste Tonics.
Resistance (1,200 treasure pieces, four diamonds): Decrease the time that Harry remains affected by bites and stings.