# 488 Ulisse Aldrovandi

the fetus emerged into the light stillborn, although it had been alive in the mother’s womb; its form is depicted in figure number IV.

In searching for the causes of these monsters, we should not immediately blame deformed parents. According to Aristotle's doctrine, children are sometimes born with defects or missing limbs from parents who are injured or mutilated, yet at other times they are born perfectly healthy.

For where the vigor of the paternal seed fails in the formation of a certain part, the spirited power of the maternal seed sometimes works to supply the defect of the paternal seed in the procreation of that limb. In such cases, however, all authors agree that mutilated monsters originate from a lack of material matter. We can distinguish between monstrous births where large body parts—such as arms—are missing, as in our current case, and those where only small parts are lacking. When large parts like arms are absent, learned men assert that such monsters arise from a deficiency of the material intended for that part’s formation. When a fetus lacks small parts, like an eye or an ear, we can confidently state that this arises from a lack of the material derived from the residue of nutrients for similar parts in the bodies of the parents.

Alternatively, we might attribute the cause of these monsters to that specific portion of the seed dedicated to generating the missing limbs, which may lack fertility while other parts of the seed retain their perfect nature. This could be because this portion of the seed did not achieve final perfection in the testes, or because its vigor was dissolved and dissipated within the womb for some reason. This leads to another explanation for this condition: when the material is unfit to receive the form of the missing limb at the very beginning of generation, it cannot be transformed into living substance. Thus, the fetus enters the world with only one arm, or with a mutilated one.

Often, however, this flaw also results from the narrowness of the womb, especially when a deformed fetus is conceived alongside a *mola* (a fleshy uterine mass) or alongside other perfect, full-sized fetuses. Furthermore, for the sake of brevity—setting aside the role of the imagination, which cannot increase or decrease physical matter—we could attribute this defect to diseases that cause a part of the fetus to be mutilated in the womb; but enough on that for now.

As for the transposition of limbs, it should be noted that the primary cause can be a poor conformation of the womb, whether natural or acquired. If, due to a tilted uterus or a tumor, the material intended to form an arm cannot expand in its proper place, it is carried to another location and attached to the neck or head, where it takes the form of an arm. Consequently, the resulting fetus enters the world with an arm or another limb transposed. Sometimes the cause can be traced to the placenta, which, adhering to the base of the uterus, usually performs the function of the liver in pregnant women. If this placenta grows larger than it should, or is displaced from its natural position for any reason, it pushes the material meant for forming the fetus away from its natural seat; this results in the monsters described above.

In this context, we must not overlook the *mola*, which is nothing more than a mass of flesh generated from corrupted seed in the womb, either before, after, or at the same time as the fetus itself. Because of its hardness, it can hinder a limb of the fetus, preventing it from taking its proper shape in its correct place and causing it instead to form in a transposed position. However, the cause of this effect can also depend on the movement and agitation of the seminal matter. If the mother, upon conceiving, is disturbed by violent movement or wandering agitation, or if she suffers a blow to the belly, the material intended for the formation of the fetus is pulled away and moved from its natural seat to another; in this way, an arm that should hang from the shoulders sometimes originates from the neck.

We do not deny that a weakness in the formative faculty plays a role in producing this effect. This is the faculty that separates the parts of the confused and raw material in the womb and sends them to their destined locations. When this faculty fails to perform its duty due to sluggishness, even if the formative power itself possesses great vigor;