Red Deer, Canada - When their Bernese Mountain Dog "Bunsen" coldly ignored his younger brother Bernoulli, their owners were worried – but things were much more serious than they thought.

What nobody suspected was that the older dog was close to death at that moment, completely unnoticed.

Together with his animal housemates Beaker, Bernoulli, and Ginger, Bunsen has gained a large following on social media in recent years.

Their owners have made it their mission to share interesting scientific facts alongside the four-legged friends' everyday lives.

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So it was nothing unusual that day when Bunsen's owner filmed him on his cell phone.

During the recording, the Canadian noticed that the Bernese Mountain Dog did not want to play with the little puppy Bernoulli, who was clinging to his side and begging for attention.

Just three days later, it became clear why Bunsen was suddenly acting so distant – the four-legged friend was seriously ill!

His owners soon noticed that his head seemed to be caving in. When he then vomited uncontrollably and could no longer lie down, they rushed him to the hospital immediately, where it was discovered that a huge cyst had grown unnoticed in the dog's body.

Even the experienced doctors had never seen anything like it, Bunsen's owners recalled in a video on Instagram.

It quickly became clear that the cyst had to be removed.

Bunsen's owners said goodbye to their four-legged friend before the operation, knowing that this might be the last time they held him alive in their arms.

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In a complicated operation, the doctors managed to completely cut out the 10-lb cyst, which had already grown together with the heart and liver.

It was later discovered that a tapeworm had caused the cyst in the Bernese Mountain Dog's stomach.

After the operation, Bunsen improved rapidly, and two months later, he was able to romp around with Bernoulli again.

His owners now realize that their dog did not reject the puppy, but tried to be there for him as he fought for his life.

"What we saw was that Bunsen's aloofness only meant that he did what he could to accept the little guy," they write on Instagram.