significance to the Mass as Sacrifice, given that Hyssop was used for the smearing of blood on the lintels at the first Passover. In the Divine Office, it was traditionally said at Lauds on all ferias; the 1911 reform restricted this use to the ferias of Advent and Lent. It is otherwise said as part of the weekly cycle on Wednesday at Matins. In the Liturgy of the Hours, it is prayed during Lauds (Morning Prayer) every Friday. A section of verse 17 is often used as the invitatory antiphon the Liturgy of the Hours. Parts of Psalm 51 are used as a responsorial psalm in both the Revised Common Lectionary and the Roman Catholic Lectionary on Ash Wednesday and on other days. Book of Common Prayer In the Church of England's Book of Common Prayer, this psalm is appointed to be read on the morning of the tenth day of the month. In English common law The Miserere was used for centuries as a judicial test of reading ability. This practice began as a means by which a defendant could claim to be a clergyman, and thus subject only to ecclesiastical courts and not subject to the power of civil courts. This was called pleading the benefit of clergy. The Biblical passage traditionally used for the literacy test was the first verse of Psalm 51. Thus, an illiterate person who had memorized this psalm could also claim the benefit of clergy, and Psalm 51 became known as the "neck-verse" because knowing it could save one's neck by transferring one's case from a secular court, where hanging was a likely sentence, to an ecclesiastical court, where both the methods of trial and the sentences given were more lenient, for example, a sentence of penance. In medicine It has been suggested that verse 7 "Purge me with hyssop, and I shall be clean:" is an early example of the medical use of Penicillium, the initial source of penicillin. Possibly since the Middle Ages (and recorded in medical literature as early as the 16th century), the supplication and submission conveyed in the psalm has been linked by some common people with the pain and despair of a patient suffering from fecal vomiting, which received the vulgar name "Miserere mei" or "Miserere", inspired by verse 3 ("Miserere mei, Deus, secundum misericordiam tuam"). The condition is a common symptom of intestinal obstruction, which, without