Though my teeth are kept usually very clean, nevertheless when I view them with the magnifying glass I find, growing between them, a little white matter as thick as wetted flour. I mixed some of this flour with pure rain water wherein are no animals, or else with some of my spittle, and then, to my great surprise, perceived that the floury matter contained many small living beasties, which moved themselves very extravagantly.

He goes on to describe their forms and motility, and confirmed his findings by studying the teeth of others, notably of two old men, one of whom is noted to have lived soberly, while the other was a "good fellow." It is with noticeable regret that he reports no obvious difference in the flora about the teeth of these two contrasting types of host.

He was a man of many interests and gave the first complete life history of the flea. He found that at one stage in its development, the pupa of the flea was attacked by "mites" and it was the communication of

by Lady Mary Wortley Montague on her return from Constantinople. Lady Mary was a restless character. She travelled widely, and letters. describing her experiences during her trip to Turkey through Germany and Austria make interesting reading. While the tongue of scandal has wagged freely about many of her activities, nevertheless Medicine owes to her the introduction of this, the first actual protective inoculation. against disease. Needless to say, there was much opposition to the method, and smallpox inoculation never seems to have been popular. It was of too strenuous a character to appeal to the popular imagination and never had any widespread use among the

masses.

which formed the basis of Dean Swift's well known lines:

"So naturalists observe the flea

Has smaller fleas that on him prey,
And these have smaller still to bite 'em
And so proceed ad infinitum."

As is so often the case with brilliant work carried out in isolated districts, Leeuwenhoek's discovery of the bacteria remained neglected for almost two centuries. Indeed the next step forward in preventive medicine was of a purely empirical nature. As you all know, inoculation with smallpox matter had been practised in the East for centuries, and this method is reputed to have been introduced into England about 1718

to medical science.

Jenner was born in Berkley in 1749, and the first part of his medical education was obtained as apprentice to a practitioner in Sodbury, but in 1770 he became a resident pupil in the house of John Hunter in London. Both were enthusiastic naturalists and a great friendship sprang up between master and pupil, and after Jenner's return to the country frequent letters passed between them, dealing chiefly with scientific topics, but occasionally having an amusing personal bearing. For example, shortly after Jenner had been jilted by his lady love, Hunter writes: "I own I was glad when I heard you was

married to a lady of fortune, but never mind her, let her go. I shall employ you with hedgehogs, for 1 do not know how far I may trust mine. A strange consolation to offer a disappointed lover, to say the least. Again, when asked to be godfather to Jenner's first child, he writes, "I wish you joy. It never rains but it pours. Rather than the brat should not a Christian I will stand godfather, for I should be unhappy if the poor little thing should go to the devil because I would not stand godfather" and so

on.

Jenner's biographer, Barron, sees him through distinctly rosy spectacles. He describes Jenner as being elegant in his attire and manner and to a degree careful of appearances. It is as such that he is shown in Northcote's portrait (fig. 5). He is seated at a table with his book The Enquiry under his hand, and in the background is the "sacred cow" from which he obtained cowpox matter, and also the figure of a child delivered from the pestilence.

His appearance suggests a man of gregarious habits, fond of conversation, and it is not hard to believe that he was generally popular. He believed in medical societies and was a valued member of two local bodies which met at various inns in the vicinity. They were popularly known as the Medico-Convivial and the Convivio-Medical Societies, and the by-laws and minutes of one of these societies are now in Sir William Osler's library, and have been bequeathed to the Royal College of

2 The hide of Jenner's cow is still preserved in the British Museum.

Physicians (London). Certain of the by-laws are of interest, especially one dealing with an age-limit for new members, and among the minutes are notes which suggest that among his friends Jenner talked so interminably about inoculation that he was generally supposed to have a bee in his bonnet as regards the cowpox.

Jenner, however, had proved to his own satisfaction that naturally occurring cowpox protected against smallpox. The next step was to show that cowpox after passage through the human subject still protected against the more serious disorder, and May 14, 1796, will always be memorable in medical history as finally marking the efficiency of vaccination. On that day he inoculated James Phipps, a boy eight years of age, with matter from the hand of Sarah Nelmes, a milkmaid who had become infected with the cowpox in a neighboring dairy (fig. 6). Later the boy was found to be resistant to smallpox when inoculated in the usual way. In other words, the great experiment towards which Jenner had been working for twenty-seven years had proved a success.

His results were communicated in a little book of seventy-five pages, entitled for short The Enquiry. The contents are chiefly case records, but it ranks with Withering's Account of the Foxglove and Beaumont's Physiology of the Digestion, as among the classics of medical literature.

In spite of some opposition, vaccination spread rapidly throughout the world, and to Dr. Waterhouse, Professor of Physic in Boston, belongs the honor of making the first report on the subject in this country. This

appeared in the Columbia Sentinel in 1800, with the vernacular title, "Something curious in the medical line."

Outside of his native land Jenner's prestige became almost legendary. Letters to Napoleon secured the release of prisoners of war. Another letter to the King of Spain restored to freedom a Toronto youth who had been captured on board a privateer off the Mexican coast.

Certificates (as below) from Jenner replaced passports when his patients travelled abroad, and gave effectual protection, as was shown on more than one occasion.

I hereby certify that Mr. A., the young gentleman who is the bearer of this, and who is about to sail from the port of Bristol on board the Adventure, Captain Vezly, for the island of Madeira, has no other object in view than the recovery of his health. EDWARD JENNER, Member of the N. I. of France

Berkeley, Gloucestershire
July 1, 1810.

In spite of his foreign influence, Jenner was deeply slighted by his treatment at home, and retired to country practice in his native town after a short sojourn in London.

And now we come to the third member of this great triad. Louis Pasteur was born in southeastern France in December, 1822, some five weeks before Jenner's death. He came of solid peasant stock, of a distinctly fighting strain. His father had been a Sergeant Major in the Napoleonic armies, and throughout the son's life we see the father's influence in his sturdy adherence to the truth.

to oblivion a disease whose very name had spread terror in every rural community. This discovery was a fitting crown to a life devoted, with unusual success, to the practical application of science, for in most cases Pasteur was able not only to identify the causative agent of the disease, but also to suggest some means for its control.

FIG. 9. PASTEUR IN HIS OLD AGE

Recognition came from all sides, medals and diplomas were showered upon him. The attitude of the lay press is also shown by the cartoons which appeared at the time, one of which is reproduced (fig. 8).

Pasteur deserves to live in our memory also for his personal qualities, his power of attracting and holding friendship, his almost infinite capacity for useful work, and, above all, his intense patriotic fervor. He was, before everything, a Frenchman. Love of country was to him a religion, and his country reciprocated with a veritable adoration, so that the name Pasteur is commemorated in some way in almost every hamlet throughout France.

In Duclaux's History of a Mind there is a picture of Pasteur in his old age, and beneath it are written two lines which may be regarded as the motto of his life:

"En fait de bien à repandre, le devoir ne cesse que là ou le pouvoir manque" or "While capable of diffusing knowledge the duty of doing so ceases only when the power fails."

From Pasteur's day the enormous strides in preventive medicine have followed in logical sequence along the lines laid down by the great master.

It is not my intention to carry the development of protective inoculation any further. The work of Russel, Wright, and many others is too well known to require comment. Suffice it to remark that the early history of this vast structure which

now call preventive medicine rests in large part on the fundamental work of van Leeuwenhoek, Jenner and Pasteur, and it is due to their labors that humanity has been delivered from the terrors of many epidemic scourges of the past.