With this introduction, we can explain what the Rambam writes at the beginning of the fifth chapter of Hilkhot Shehitah, where he begins by writing: “the tereiphah referred to in the Torah is an animal on the verge of death, and the Torah speaks of ‘tereiphah’ i.e., an animal that was mauled by a predator, because the Torah speaks about the most common circumstance (דבר הכתוב בהווה) in which an animal is brought to the verge of death by a predator.”
In this passage, the Rambam does not mention derusah, because the term “tereiphah” does not denote the injection of poison by a predator into its prey, only tearing and battering and the like. Moreover, the condition specified by the Rambam that the animal be on the verge of death proves that poisoning is not implied by the term “tereiphah.” A drop of poison injected by the predator into its prey is not sufficient to cause the imminent death of the prey. Moreover, the Rambam writes immediately thereafter (Id. 2-3): “There are also other maladies that can cause death, and the following eight tereiphot were transmitted to Moshe at Sinai: derusah, nequvah, haseirah, netulah, pesuqah, qeru’ah, nephulah, shevurah).“ Thus, the Rambam counts derusah among the “other maladies” added by the Halakhah to the tereiphah of the Scripture. So, the tereiphah of the Scripture could certainly not include poisoning, but only an animal brought to the verge of death by an external cause affecting its vital organs. That is why the Rambam says that tereiphah is not caused only by an attack by a predator, the Torah speaking only of the usual occurrence.
The point is also elucidated by the Rambam in Ma’akhalot Assurot where he asks rhetorically what difference there is between an attack by a predator and some other external cause of the imminent death of an animal. His rhetorical question certainly could not have been referring to derusah, but only to tereiphah, because he wrote there (Id. 4:8):
We do not distinguish between animals that died based on the cause of death, whether it died naturally, fell and died, was strangled until it died, or was fatally attacked by a predator. Similarly, we do not distinguish between animal that are on the verge of death, whether it was mauled by a predator, fell from the roof and broke the majority of its ribs, fell and crushed its limbs, was shot with an arrow that pierced its heart or lung, developed an illness that caused its heart or lung to be perforated, broke the majority of its ribs, or the like. If it is on the verge of death regardless of the cause, it is a treiphah.
So, by saying that the Torah mentioned the most common occurrence, the Rambam meant that what defines a tereiphah is that an external cause has brought the animal to the verge of death, because there is no reason to distinguish between injury by a predator, or falling from a roof, or being shot by an arrow to the heart. But the injection of posion into an animal — unless it was brought to the verge of death by the poison — is not what the Scripture meant in the verse “בשר בשדה טרפה”. If, therefore, someone eats the flesh of an animal that suffers from one of the tereiphot enumerated by the Halakhah, he cannot be punished with lashes, because those tereiphot are not the tereiphah forbidden by the Scripture, but are only supplements of the Halakhah to elaborate on the verse “זאת החיה” in which a positive commandment is stated, thereby implying a prohibition, but a prohibition whose violation does not entail punishment by lashes.
The maladies identified by the Halakhah as tereiphot must be understood as supplements to the verse “זאת החיה”, rather than to the verse “בשר בשדה טרפה”. If the Halakhah were elaborating on the latter verse, teaching us that if an animal injected with poison from the claws of a predator, its flesh is Biblically prohibited as tereiphah even though the poison has not brought the animal to the verge of death, then the principle articulated by the Rambam that there is no distinction between the external causes that render an animal a tereiphah would be negated, because derusah would show that an animal is a tereiphah regardless of whether the malady brings the animal to the verge of death. That is why the Rambam distinguished between derusah and the other seven types of malady that, according to the Halakhah, render an animal a treiphah, because derusah, unlike the other tereiphot enumerated by the Halakhah, is most commonly the result of a predator’s attack on its prey, even though a predator’s attack might also tear or puncture a vital internal organ, while a predator’s attack would not be the most common cause of the other tereiphot enumerated by the Halakhah.
We apply the fixed rules of the Halakhah to establish what is a tereiphah without regard to the Biblical requirement that an animal be on the verge of death, because the Halakhah demands that any animal be considered a tereiphah, even if it is not on the verge of death, if it has any of the enumerated defects, regardless of whether the animal will in fact die as a result of those conditions. Thus, even according to those that hold the opinion that a tereiphah cannot survive, the status of tereiphah does not depend on whether the animal can survive, because whenever one of the categories enumerated by the Halakhah is detected in an animal, it becomes a tereiphah even if it can survive. The dispute between those who hold the opinion that a tereiphah can survive and those holding that it cannot survive concerns only whether surviving 12 months resolves a doubt about whether the animal suffers from any malady that, according to the Halakhah, renders the animal a tereiphah. But resolving this doubt wasn’t the concern of the verse “בשר בשדה טרפה”. Thus, the Rambam in his wisdom wrote that the seven categories of tereiphah other than derusah are treated more leniently than derusah even though they are all known to us only as halakhot le-moshe mi-sinai, derusah being undeducible from the Scripture, because “tereiphah” does not mean, nor does it imply, “derusah.”
And if we supposed that the Halakhah came to interpret the verse to teach us that “treiphah” does imply “derusah,” so that poisoning automatically renders an animal a treiphah, thereby rendering the consumption of the flesh of such an animal a Biblical violation punishable by lashes, then how would we be able to infer the other seven categories of treiphah are prohibited? Even if we were to say that a predator might sometimes cause the puncture of an internal organ while mauling its prey, those types of tereiphah certainly would not normally be caused by a predator’s attack. Why then would the Scripture have spoken of a predatory attack as the basis for deriving all these other kinds of tereiphah? The Rambam therefore referred only to derusah, saying that the Sages were more stringent in connection with derusah than the other seven tereiphot, because derusah can more easily be associated to the verse “בשר בשדה טרפה” than the other enumerated tereriphot which have no association at all to the verse.
But lashes would not be administered to one who consumes the flesh of a derusah, because there is no essential distinction between derusah and the other seven categories, none of which are entailed by the Biblical prohibition of “בשר בשדה טרפה”, which includes only the flesh of animals on the verge of death regardless of cause. The Halakhah that identifies the eight categories of tereiphah that don’t necessarily bring an animal to the verge of death therefore supplement the Scripture having the status of divrei soferim, for whose violation one may not be punished by lashes.
The truth is that, as has been written above, that rules like those concerning tereiphot are not scientific at all, because medical knowledge cannot establish fixed rules for each animal species, for man and beast, fish and fowl, for a small child, an old person, or a mighty person at the peak of his strength. This is not scientific, just as with respect to other quantitative guidelines of the Torah, such as the age of adulthood in males and females, and the minimum amount of food that satisfies the craving for food, science does distinguish between different persons and different foods. The same principle applies here that the rules are established by Halakhah and not by scientific knowledge. And lashes cannot be administered for violating the Halakhic rules of tereiphot, because lashes are administered only for eating the Biblically prohibited flesh of an animal on the verge of death.
We can now understand why the Rambam discussed all the 18 treiphot of Halakhah in Hilkhot Shehitah rather than in Hilkhot Ma’akhalot Assurot which would have been the more logical place for that discussion if the Rambam had believed that the 18 tereiphot are an explanation of the verse “ובשר בשדה טרפה”. The Rambam, however, believed that the 18 tereiphot don’t explain, but supplement, the Scripture and the 18 treiphot are linked (דרך אסמכתא) to the verse “זאת החיה”. Nor were the 18 tereiphot transmitted in the desert, but were introduced with the Halakhah that R. Yesheivav received from R. Yehoshua that even a minimal defect in the simanim invalidates an otherwise proper shehitah, a Halakhah linked to the verse “כאשר צויתיך”, which means that they were commanded to perform shehitah on Hullin as well as qodshim just before entry into the Land, when nehirah was invalidated. But in the desert when they were performing shehitah only on qodshim, a shehitah was not invalidated by a minimal defect in the simanim.
Similarly, the Rambam at the beginning of Hilkhot Shehitah lists, as is his custom, all the commandments discussed in that book: five commandments, three of which are positive and two negative. First, to perform shehitah before consuming meat; not to perform shehitah on an animal and its offspring in the same day; to cover the blood spilt in performing shehitah on a wild animal or a fowl; not to take a mother bird that hovers over her unhatched eggs or chicks; to send away the mother if one has taken the mother from her chicks. But how could the Rambam have disregarded the Biblical prohibition against eating the flesh of a tereiphah when he devotes seven chapters to the laws of tereiphah as part of Hilkhot Shehitah? There can thus be no doubt that the Rambam did not consider the laws of tereiphot discussed in Hilkhot Shehitah to be an explanation of the law of tereiphah in the Scripture, but an explanation of the Halakhah that was introduced upon entry into the Land along with the Halakhah that even a minimal defect in shehitah invalidates the shehitah.