(14) Unequal Double Monsters, Foetus in Foetu
There are some well-authenticated instances of this most curious of all anomalies. The most celebrated of these parasite bearing monsters was a Genoese, Lazarus Johannes Baptista Colloredo, born in 1716, who was figured as a child by Licetus, and again by Bartholinus at the age of twenty-eight as a young man of average stature. The parasite adhered to the lower end of his breast-bone, and was a tolerably well-formed child, wanting only one leg; it breathed, slept at intervals, and moved its body, but it had no separate nutritive functions.
The parasite is more apt to be a miniature acardiac and acephalus fragment, as in the case of the one borne in front of the abdomen of a Chinaman figured by I. Geoffrey St-Hilaire.
Sometimes the parasite is contained in a pouch under the skin of the abdominal wall, and in another class (of which there is a specimen in the Hunterian Museum) it has actually been included, by the closure of the ventral laminae, within the abdominal cavity of the foetus, -- a true foetus in foetu.
Shapeless parasitic fragments containing masses of bone, cartilage, and other tissue are found also in the space behind the breast (mediastinal teratoma), or growing from the base of the skull and protruding through the mouth ("epignathous teratoma," appearing to be separated on the jaw), and, most frequently of all, attached to the sacrum.
These last pass by a most interesting transition into common forms of congenital sacral tumours (which may be of enormous size), consisting mainly of the kind of tissue having its physiological type in the curious gland-like body (coccygeal gland) in which the middle sacral artery comes to an end.
The congenital sacral tumours have a tendency to become cystic, and they are probably related to the more perfect congenital cysts of the neck region, where there is another minute gland-like body of the same nature as the coccygeal at the point of bifurcation of the common carotid artery.
Other tumours of the body, especially certain of the sarcomatous class, may be regarded from the point of view of monstra per excessum; but such cases suggest not so much a question of aberrant development within the blastoderm as of the indwelling spontaneity of a single post-embryonic tissue; and they fall to be considered more properly, along with tumours in general, in the article PATHOLOGY (q. v.).
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