James Jurin wrote Letter L-586 to introduce Matthew Raper to Leeuwenhoek and continue the discussion about blood globules and generation

July 6, 1723

The date is New Style, which was eleven days ahead of the Old Style date of 25 June 1723 used by Jurin in London.

In this letter, Jurin introduced a Mr Raper, delivering the letter, as someone who would like to witness some of Leeuwenhoek’s observations. It is unclear whether it was the father or the son named Matthew Raper who who Jurin was recommending. The father, Matthew Raper (1680-1748), was a businessman involved with the East India Company and the importing of Chinese silks. His son Matthew Raper Junior was born in 1705. That would have made him 18 when he was introduced to Leeuwenhoek. He became an astronomer, mathematician, director of the South Sea Company, and, after 1754, a fellow of the Royal Society. He died in 1778. 

Jurin then thanked Leeuwenhoek for his work on the size of blood globules, which Jurin had suggested, and asked Leeuwenhoek to study them further.

Jurin noted that Leeuwenhoek's work had led to the overthrow of the old theory of generation, but that perversely contemporary anatomists were now using his observations to support the old theory.

He briefly mentioned Leeuwenhoek's health.


The manuscript is to be found in London, Wellcome Library MS 6143, 4 pp.

Crane Court, London
June 25th 1723

Honoured Sir,

As my Worthy & very particular Friend, Mr Raper, from whose hands you receive this, was going for Holland & was curious of waiting upon you, & being an Eye Witness of some of your Curious Observations; it was upon his account, that I deferr'd replying to ye Letter you were pleased to honour me with of ye 19 of March last, as likewise to that of Jan. 1721 directed to ye Royal Society. In this lnterim your Letter to ye Society of May 31st 1723 came to my hands.

I need not tell you, Sir, that all these Letters were kindly receivd by ye Royal Society, that they order'd their solemn thanks to you to be recorded in their Journals, & to be return'd by their Secretary, since ye constant marks of Esteem & affection, wch they have paid you for upwards of fifty years, must have abundantly convinced you, that notwithstanding ye perpetual succession of different Members, yet ye Sentiments of ye Body wth regard to Mr Leeuwenhoek can never alter.

I am very much obliged to you, for ye trouble you have been pleas'd to take in examining my Observation about ye magnitude off Blood Globules which I am glad to find confirm'd by your determination. This I look upon to be no indifferent or unusefull Speculation since it is not impossible but that observing ye Magnitude of the Blood Globules in different Animals together wth that ofye minute Vessels, particularly in ye Lungs, may some time or other lead us to discover, where, & by what means these Globules are formed, & why they keep to one determinate bigness in ye same Animal. This, Sir, is an Inquiry not unworthy of your pursuit, as well as what you have ye best Title to, these Globules being oue of ye great Discoveries, for which ye World is indebted to your indefatigable Diligence & Penetration.

By a Passage in your last, I find, I was not so happy in Speaking of ye Ovarium, as to express myself with sufficient clearness to be understood. I have long ago acquainted myself with your curious Observations & Sentiments about Generation, wch I look upon to be ye most solid & instructive of any thing, that has been publish'd upon that Subject. You had thereby entirely overthrown ye old doctrine of Generation, but you are not ignorant, that some Eminent late Anatomists have founded a new System upon ye Basis of your Discoveries, & have maimain'd, that an Ovum is ye proper Nidus, wherein ye Animalculum in Semine Masculino is lodged & nourished, & that ye Ovum thereby impregnated, is afterwards detached from ye Ovarium, & is convey'd thro' ye Falloppian Tube into ye Uterus. This is ye Doctrine of ye Ovarium, of which I said, that your late Observations seem'd to sap & overthrow ye very Foundation.

I am very glad to find you are so well recovered from your late Illness, wch I think, you rightly judged not to consist in ye Palpitation of ye Heart from ye Regularity of your Pulse, but rather to be seated in ye Diaphragm. I heartily wish ye continuance of your Health for still many Years, to ye advancement of Learning & Philosophy which owe so much to your Observations. I am Learned Sir

Your must faithfull humble Servant
J. Jurin