Autopsy.

I’m almost finished with Richard Tarrant’s Texts, Editors, and Readers (1, 2, 3), and I was brought up short by this passage in the concluding chapter: “some particularly important manuscripts – including the Codex Venetus A of Homer – can be studied in greater detail in digitized form than by any other means, including autopsy.” Of course I was aware that autopsy is from Greek αὐτοψία ‘act of seeing with one’s own eyes’ (which is why Stan Brakhage called his disturbing 1971 film about forensic pathologists The Act of Seeing with One’s Own Eyes), but I hadn’t known that that sense was used in English. A trip to the OED (entry revised 2011) proved enlightening:

1. The action or process of seeing with one’s own eyes; personal observation, inspection, or experience. Now rare.

1607 It is apparently knowne, especially to them which are skild in the autopsie of Anatomie, the seat or fountaine head of it, is..a great hollow veine.
T. Walkington, The Optick Glasse of Humors. Or The Touchstone of a Golden Temperature, or The Philosophers Stone to Make a Golden Temper f. 59

1647 For we question whether..a man by the bare light and instruction of the Book could attaine to a dextrous practice of a trade, whereunto hath been required seven yeares Autopsia.
W. Petty, Advice to Hartlib 19

1651 Or by autopsie [Latin per autopsiam], when by our observation, wee get a certaine knowledge of things.
R. Wittie, translation of J. Primrose, Popular Errours i. xiv. 53
[…]

1722 The extreme Capillaries of these Vessels are not to be prov’d by Autopsy, no more than those of the Veins and Arteries are.
J. Wainewright, Anat. Treat. Liver 60
[…]

1818 It is also this kind of evidence which places beyond dispute the autopsy of a traveller; and distinguishes him from the mere writer of Travels, who never himself saw what he relates.
E. D. Clarke, Trav. Europe, Asia & Afr. Part III (1824) vol. IX. p. viii

1839 The defect of autopsy may be compensated by sufficient testimony of a multitude.
T. De Quincey, On Hume’s Argument in Blackwood’s Edinburgh Magazine July 95/2

1901 The evidence..that he is describing from personal autopsy the scenes of the great events which he narrates is overwhelming.
G. B. Grundy, Great Persian War & Preliminaries vi. 223

1988 [He] has collated (usually from photographs or facsimiles, only rarely by autopsy) all the manuscripts cited except for [etc.].
Classical Philology vol. 83 151

2003 Pliny was procurator of Hispania Tarraconensis, and the Natural History contains information about the area which Pliny seems to have derived from autopsy.
J. N. Adams, Bilingualism & Latin Language iv. 450

Sense 2.a., “Examination of the organs of a dead body in order to determine the cause of death, nature and extent of disease, result of treatment, etc.; post-mortem examination; an instance of this,” only goes back to 1805 (“The distinguishing signs of peripneumony and pleurisy are so uncertain that they have been doubted by some celebrated physicians; they have been so often belied by cadaverous autopsia,” Philosophical Magazine vol. 21 240). I note, more in anger than in sorrow, that they once again show their indifference to authorship; the 1988 citation under 1 is by Donald J. Mastronarde, and the 2.a. citation is from “An Essay on Medical Entomology” by François-Pierre Chaumeton.

The etymology goes into commendable detail on the sense development:

< (i) post-classical Latin autopsia act of seeing with one’s own eyes, careful visual examination (1586 or earlier in a medical context), careful visual examination of a patient for the purposes of diagnosis (1605 or earlier in medical contexts),

and its etymon (ii) Hellenistic Greek αὐτοψία act of seeing with one’s own eyes, in medical contexts (e.g. in Galen) also with reference to careful visual examination of a patient for the purposes of diagnosis < Byzantine Greek αὔτοπτος self-revealed (although this is apparently first attested slightly later (4th cent. a.d.); < ancient Greek αὐτο- auto- comb. form¹ + ‑οπτος: see optic adj.) + ‑ία ‑y suffix³; compare ‑opsy comb. form.

In sense 2a probably after French autopsie post-mortem examination (1671 or earlier (and now chiefly) in this sense: see below; 1801 or earlier in (now disused) autopsie cadavérique, 1821 or earlier in (rarer and now obsolete) autopsie cadavéreuse; 1594 in Middle French or earlier in sense ‘careful visual examination of a patient for the purposes of diagnosis’; the general sense ‘action or process of seeing with one’s own eyes’ is apparently not paralleled in French until later: 1640, in a scientific context). Compare German Autopsie (1750; early 19th cent. (and now chiefly) in sense 2a).

Notes
French autopsie is attested in 1573 in Middle French (in a medical context), and subsequently in 1665, in two instances which recent authoritative dictionaries of the language assign to the sense ‘post-mortem examination’. However, the context of the 1573 instance (as given in Trésor de la langue française at autopsie and the source cited there, C.-A. Desmaze Curiosités des anciennes justices (1867) 128) does not make the precise sense clear, and the 1665 instance is cited in Le français moderne vol. 14 290 (and hence in Französisches etymol. Wörterbuch vol. XXV. 1117/2) without any context at all, in a list of scientific terms used by a 17th-cent. French physician in his unpublished letters. In view of these facts, of the widespread objections on religious grounds to post-mortem examinations before the 18th cent., and of the scarcity of French instances of the sense ‘post-mortem examination’ before the early 19th cent., it seems more likely that the sense at least in the first of these two instances was ‘careful visual examination of a living patient’.

For a piece of peevery (is it still current?) about how “Technically you can’t perform an autopsy on a different species,” see this 2008 post.