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The phrase to poison the wellspring of something means: to corrupt the very essence of something.
This phrase has particularly been used in theological contexts. The following, for example, is from Dodgy theology fans the flames of human suffering, by Ron Ferguson, published in The Press and Journal (Aberdeen, Aberdeenshire, Scotland) of Tuesday 15th August 2006 [page 14, column 3]:
At its best, religion provides illumination, inspiration and generosity. At its worst, it poisons the wellsprings of human life.
These are, in chronological order, the earliest figurative uses that I have found of the phrase to poison the wellspring, and of extended metaphors relating to the pollution of fountainheads:
1-: From Joseph’s Consideration: A Sermon, preached in Clare-Hall Chapel, on Monday, February the 29th, 1808, [&c.] (Cambridge: Printed by Francis Hodson, 1808), by the English clergyman and playwright James Plumptre (1771-1832) [page 23]:
Of the same nature with indecent conversation is the singing or attending to indecent or corrupting songs. The practice indeed were worse, were it as general as conversation; since, when heightened by music, by wine, and by company and mirth, the impression is more strong and lasting, and the mind becomes more fully and fatally polluted. Deadly is the crime of administering poison to destroy the body of another; greater is his wickedness, who shall poison the well-springs from which multitudes drink, and from which they should receive nourishment and health; but deep is the damnation of contaminating and killing the soul, of poisoning that fountain out of which should arise the issues of life, spreading like a fruitful stream, and diffusing joy, health, purity, and fertility to all within the influences of its course.
2-: From The Edinburgh Annual Register, for 1810 (Edinburgh: Printed by James Ballantyne and Co., 1812) [The History of Europe, 1810. Chap. XI. Spain. Conduct of the Central Junta. Plan for their overthrow disclosed. Romana’s Attack upon them, and their Defence, page 366, column 2]:
To poison food or water in time of war, is a practice which all people, who are not absolute savages, have pronounced infamous by common consent; but it is a light crime compared to the damnable means which Buonaparte employed for the subjugation of Spain,—means which poisoned the well-springs of social order, and loosened the very joints and fibres of society.
3-: From Sermons preached in the Cathedral Church of St. Peter, Exeter, by the late Rev. Thomas Grylls, A.M., of Trinity College, Cambridge, Prebendary of Exeter, and Rector of Cardynham, Cornwall (London: J. Hatchard and Son, 1815) [Sermon V. Unbelief the Great Cause of Gospel Failure, page 88]:
There can be little difficulty in tracing the several polluted streams which by their admixture poison the well-spring of life itself, to one common source—“an evil heart of unbelief.”
4-: From The Sun (London, England) of Tuesday 23rd January 1816 [page 2, column 4]:
It is intimated that M. Pozzo di Borgo means to prosecute with the utmost rigour the forgery of which he thinks he has discovered the author. It is said, too, that he considers that shameless manoeuvre as only a ramification of an extensive plot, for the abusing the public opinion of Europe, by false and calumnious publications; and expects that some of the papers seized in the investigation of Lavalette’s affair, will throw great light on the other, and more pernicious conspiracy.—Most heartily do we wish him success in this undertaking. Those who abuse a free press by systematic forgery, are among the deadliest enemies of liberty: they poison the well springs of information.
5-: From a transcript of the debates that took place in the House of Commons on Friday 14th March 1817, published in The Courier (London, England) of Saturday 15th March 1817 [page 3, column 3]:
Mr. Canning said, […] there could not, in his opinion, be a greater enemy to mankind than he who by taking advantage of the pressure of the distress of the people, and the increased means of knowledge placed within their reach, called it in doubt whether the communication of knowledge had been useful or detrimental to the community. This malignity in extent exceeded every other—it poisoned the well springs of life—it palsied the efforts of benevolence, and tended to deprive future generations of one of the greatest blessings which a nation could enjoy.
6-: From Some Account of Thomas Brown, the Elder, by Shaw Tonkin, dated Mevagizzey, Cornwall, 3rd April 1819, published in The New Monthly Magazine, and Universal Register (London, England) of Tuesday 1st June 1819 [page 412, column 1]:
When filthy ideas go abroad, in coarse and vulgar language, they carry their antidote with them, and can do little harm; but when they are bodied in a graceful form, and set forth with all the charms and graces of poetry, they insinuate into the mind, seize upon the imagination, and completely poison the well-springs of life.
7-: From John’s Lamentations to his Cousin in the Country, by ‘John Bull’, published in The Morning Chronicle (London, England) of Saturday 23rd December 1820 [page 3, column 2]:
Heaven’s decrees most distinctly appear:
For Heaven, offended, abandons the cause
Of oppression, injustice and infamous laws.
All good shall be evil, fair peace shall be strife,
With a system that poisons the well-spring of life:
Tho’ fertile our meadows, and teeming our flocks,
The plenty’s like that, which starv’d Tantalus mocks.
8-: From the Birmingham and Lichfield Chronicle (Birmingham, Warwickshire, England) of Thursday 11th January 1821 [page 3, column 1]:
It is with pleasure and pride that we announce the formation of a Society in London for the maintenance of order, the support of the due execution of the laws, the restraint of those blasphemous and seditious publications which are now actively circulated, and the dissemination of sound Constitutional principles in Church and State. […] Disaffection, if thus assailed, will soon hide its head; and our beloved country, freed from the venomous animals which now disturb her quiet and poison the well-springs of her prosperity, will soon “see her wholesome days again.”
9-: From On the Scepticism of Gibbon, by ‘J. W.’, dated Friday 15th February 1822, published in The Imperial Magazine; Or, Compendium of Religious, Moral, & Philosophical Knowledge (London, England) of May 1822 [page 440]:
We see the ungovernable spirit which, in after life, ventured to attack the foundations of moral order, and to poison the well-spring of private happiness.
10 & 11-: From accounts of the trial of “the proprietors and printer of the John Bull newspaper, for libels upon Her late Majesty Queen Caroline”, which was held at the Court of King’s Bench, Westminster, on Friday 17th May 1822:
10-: From the account published in The New Times (London, England) of Saturday 18th May 1822 [page 3, column 5]:
Mr. Brougham—[…] They have polluted the public press; they have degraded that best instrument of public instruction; and one of their boasts is, the large mass of pollution which they have infused into the public mind. If we hold, and hold justly, him to be the worst of malefactors who poisons the wells of a large city, shall we not deem the man guilty of a grave offence who poisons the fountain of public instruction?
11-: From the account published in the British Neptune; Or, Naval, Military, and Fashionable Advertiser (London, England) of Sunday 19th May 1822 [page 160, column 2]:
Mr. Brougham—[…] They had degraded the press, that best instrument of public instruction, and had made it their boast that they introduced into it one mighty mass of corruption. If they were holden to be the most atrocious of criminals who poisoned the wells of a great city, what should be said of those who infected the springs of knowledge at the fountain head, and made its waters fit only for unnatural and degraded appetites to banquet on?
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