For the source text click/tap here: Zevachim 35
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The Mishna on our daf teaches that this law only applies in a situation where the inappropriate thought refers to something that is ordinarily eaten. If the inappropriate thought was about a part of the animal that is not normally eaten, e.g. bones, hooves, sinews, horns, etc., then the sacrifice would not be affected.
In the continuation of the Mishna we learn that if the sacrifice was a female and the inappropriate thought related to its unborn fetus or to the placenta itself, the korban is unaffected. Similarly, if the thought was to eat the unborn eggs of the sacrificial bird or drink the milk of the animal that was to be brought as a korban, it would not affect the sacrifice.
We explore the embryo and placenta in Ancient Near East and newer iterations.