Skybird your logic is sound. Venoms do different things though.
Some begin to dissolve tissue, others shut down the nervous system, others target respiration or impair heart function.
I think in this case, any cat of about 5 lbs or less would have experienced symptoms inside of 30 minutes.
Lethargy
Extreme thirst
Irregular breathing
Lack of coordination
Dizziness
Unusually dilated pupils
If the cat has made it this long it's out of the woods. If a brown snake hit that kitty it would be dead by now.
As they say... 9 lives
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