HYPOSTASIS. 409 HYPSIPYLE, Loofs (Halle, 1803); and Fisher (Xew York, ISllll). See TRI.MTY. DorTRI.NE OF THE. HY'POSTAT'IC UNION". A term used to describe the union of Clirist's human nature to the hypostasis or person of God the Word, in virtue whereof, wliile each nature is eoniplotc, oven after union, yet there is but one undivided person of the God-man, to which all the actions, whether divine or human, arc ascribed. This form of expression was devised for the purpose of excludinjr the doctrine of a mere moral union held by Ncstorius. See Monopiiysites ; Xes- ToRiAxs; Trinity, Doctri>'E of the. HYPOSTJL'PHITES. See Thiosulphuric Acid. HYPOT'ENUSE (Fr. hi/potenuse, from Gk. u-orcivovaa, htjpoteinousa, subtending, from irroreivciv, hj/jioteinein, to subtend, from i/jr6, hypo, under + Tiiven; fcijieiii, to stretch). That s^ide of a right-angled triangle opposite to the right angle. The hypotenuse is the longest side of the triangle, and its mid-point is the centre of the circumscribed circle. According to the famous 47th proposition of the first book of Euclid's Elements: The square of the hypot- enuse of a right-angled triangle equals the sum of the squares on the other two sides; the proof of this proposition is attributed to Pythagoras. HYPOTHEC A'TION (ML. hypothecatio, from hi/pothccure. to hypothecate, from Lat. hi/po- llirca. from Gk. i-oOz/nrj, hypothi-ke, pledge, from vTTOTiBivai, hypotithcnai, to place under, from virb, hypo, under + -iSivai, titheitai. to place). At Ro- man law hypothec was the right to take and sell property belonging to another to satisfj' a claim. Any balance (hyperocha supcrfUtum) remaining after a creditor's claim was satisfied was restored to the former owner of the property. Hypothec might be established by the act of the owner (English' mortgage) , or it might be created by law (English lien). In either case the hypothe- cation might be of real property or of personal property, or of both. Many of the legal liens ex- tended over the debtor's entire estate, real and personal. Hypothec was distinguished from pig- nus or pledge, in that it was established without delivery of possession. In modern civil law the term hypothoc is commonly restricted to the mortgage or lien upon real property. At French law a lien upon movables or upon an entire es- tate is termed a 'privilege.' In Spanish law the term is restricted to the contractual mortgage of real property: all legal lien.s, whether upon realty or personalty, are 'preferences.' In Scot- land, however, a legal lion upon personal prop- erty is called a hyjinthec. Consult the authori- ties referred to under Real Pkopebty. HYPOTH'ESIS (Gk. ivdeeaic , supposition, from i-orMmi, Injpotithrnni. to place under, from i~6, hypo, imder + nSivai, titheiiai, to place). In scientific procedure, a conjecture as to the explanation of any phenomenon, made pro- visionally and used as a starting-point for fur- ther investigation and theor'. Thus in studying (he motion of the moon Newton made the hypothesis that its divergence from the straight line was due to the same cause that brings an apple to the grotmd when released from the stem. He then proceeded to find whether the rate of fall in the two cases was expressible by some single formula. After years it was dis- covered that this was the case. It is now quite generally admitted that an hypothesis, to have any value, should be based on some known law, and should be the conjectural extension of that law to a new sphere under investigation. Thus Xewton worked from the known law of gravita- tion on the surface of the earth. The hypothesis of a luminiferous ether is based on the known laws of the motion of fluids, etc. Such a known law is called a vera causa. Some logical purists insist not only that the point of departure must be a known law, but that the extension of this law to another sphere may not be legitimately made un- less its extension is at least conceivably verifiable by sense-perception. Thus they claim that the existence of the luminiferous ether is not a rigidly logical hypothesis, because the ether is thought of as having no properties perceivable by our senses without the use of instruments that no one even supposes capable of construction. Such an interpretation of the vera causa is, how- ever, not in accordance with actual scientific practice, nor is it theoretically justifiable. It would rule out the hypothesis of the prevalence of gravitation even within the solar system, as no one ever did or presumably ever will perceive with any of his senses the action of gravita- tion except as a movement, and this movement is the thing to be explained by the law of gravita- tion, and not its further perceptual justification. An hypothesis is a provisional attempt to think things together as instances of the prevalence of the same law; and all that is necessary to make an hypothesis valuable is that it should furnish some conception which shall at least provisionally unify experience by reducing it to law. A distinction is often made between theory and hypothesis. A theory is said to be a verified hypothesis. This distinction is one of degree, not of kind. Even an hypothesis which has been 'verified' may be overthrown by new facts; so that it is rather the fashion nowadays to speak of all the conceptions of natural science as 'irorkiny hypotheses,' and to say that they are accepted only tentatively as the basis for further investigations and for further theorizing on re- sults. As to whether there is any unconditional clement in scientific conceptions, see Knowledge, TiiEORV of. For bi1)liography of the subject, see the works cited in the article I.0(MC. HYPOTHETICAL QUESTION. A legal term for the proper form of question to be asked an expert witness. See Evidence. HYPOXANTHIN, hl'p<'. zan'thin (from Gk. Ovo^afffoc, hypoxantlios, yollowish-brown, from uirA, hypo, under + {o^Wf xanthos, yellow), or Sarkin, C.,H)X,0. An organic substance chemically allied to .anthin, which it usiially accompanies. If given to birds, hypoxanthin is excreted largely in the form of uric acid ; it is not known by what organ this transformation is efTected — probably not by the liver. See Xantuin. HYPSIPYXE, hip-sipl-le (Lat., from Gk. 'Ti/'iTiiX?)'). The daughter of Thoas of Lemnos. whom she saved when the women of the island killed all the other men in revenge for their neglect. When the Argonauts came to Lemnos, Hypsipyle became by .Tason the mother of two sons. Euneus and Xehrophonus or Thoas. Hav- ing been driven o>it because she had spared her father. Hypsipyle l)eeanie the nurse of Opheltes, son of the Arcadian King Lycurgus. When
