Comentario sobre Yevamot 7:1

אלמנה לכ"ג: עבדי מלוג – what the woman leaves for herself and does not write in her Ketubah is called

If a widow [who married] a high priest, or if a divorced woman or a halutzah [who married] an ordinary priest brought in to her husband melog slaves and tzon barzel slaves, the melog slaves may not eat terumah but the tzon barzel slaves may eat of it.
The following are melog slaves: those who, if they die, are the wife’s loss and, if their value increases, are her profit. Even though it is the husband's duty to maintain them, they may not eat terumah.
The following are tzon barzel slaves: if they die, they are the loss of the husband and, if their value increases, they are a profit to him. Since he is responsible for them, they are permitted to eat terumah.
The slave of a kohen is allowed to eat terumah, which can only be eaten by kohanim and those under their domain (Leviticus 22:11). Our mishnah discusses the issue of slaves brought into a marriage by the wife as part of her dowry, in a case where the marriage was against the halakhah and therefore she herself cannot eat terumah.
When we learned mishnah 4:3, we discussed the terms “tzon barzel” and “melog” or “pluckable property”. This is what I wrote there:
Dowry can come in two forms. The first form is called “pluckable property” (nikhse melog). This is money that she brings from her father’s house that remain hers and the husband may not use. The husband has rights to the profit earned from this money during the marriage. He has no responsibility for the money. For instance, if she brings in a piece of land, the land is hers but the husband may use the fruits of the land. If the land should be taken by the Romans, he is not responsible to pay his wife the value of the land. Money that she receives as a gift or as an inheritance is part of this category.
The second form is “property of iron sheep” (nikhse tzon barzel). This is written in the ketubah and hence the husband has responsibility for it, should the property be lost, stolen or destroyed. The husband may use the property. His sole responsibility is to return the value of the original property upon death or divorce.
Section one: In the case of our mishnah, a woman who is not allowed to marry a kohen, nevertheless goes ahead and marries him. When she has intercourse with him, she becomes a halalah, a woman profaned from the priesthood, and she can no longer eat terumah, neither in her husband’s home nor in her father’s (if he was a kohen). Since she can no longer eat terumah, her slaves can also no longer eat terumah. The mishnah teaches that since tzon barzel slaves belong more to her husband than they do to her, they may eat terumah. Melog slaves, who belong more to her than to him, cannot eat terumah.
Section two: This section discusses the difference between melog and tzon barzel slaves. Melog slaves belong to the woman, although while the marriage is still going they work for the husband. The fact that they belong to the woman means that if they die it is her loss, and if they go up in value, it is her gain. Despite the fact that the husband must maintain them with food, clothing and shelter, they still belong to the woman. Since she cannot eat terumah due to her forbidden marriage, they too cannot eat terumah.
In contrast, tzon barzel slaves belong to the husband, and his only obligation is to pay their value back to the woman upon the termination of the marriage through death or divorce. If they die, he must still pay back the value. If they appreciate in value, it is his profit. Since he is responsible for their worth, meaning that if something happens to them he must pay back the woman for the loss, they may eat terumah.
In summary, the mishnah defines ownership by who profits or loses when the value of the slaves rises or falls. The obligation to maintain the slaves does not cause the husband to be the owner.

נכסי (עבדי) מלוג – a wife’s estate of which the husband has the fruition without responsibility for loss or deterioration - that the husband “plucks” that property like the plucking of chickens because he consumes the fruits of those properties and if they lessened [In value] they lessened for her, and if they increased, they increased for her. But נכסי צאן ברזל (mort-main, the wife’s estate held by her husband, which, in the case of her death or divorce, he must restore “in specie,” being responsible with all his landed property for loss or deterioration) – they are the properties that she brought in to him and what he adds to it is hers, and they wrote into the Ketubah: the total amount that so-and-so accepted upon himself is such -and such, in her Ketubah, and therefore, they are called צאן ברזל – as the principal exists like iron, and if everyone died, the husband is liable to because they are accustomed to place the sheep in such-and-such an appraisement of valuables (brought into the marriage by the wife) , and the shepherd would be responsible for them (if lost), according to the estimate even if all the sheep died, hence, they are called properties that the husband accepts responsibility for - נכסי צאן ברזל (that must be returned to the wife “in specie” in the event of death or divorce.