Makers of Modern Medicine. James Joseph Walsh

for truth as it could be deduced by observation and experiment.

      It was to Hunter that Jenner once wrote that he had heard it said in Gloucestershire that the dairy workers who suffered from a certain disease caught from the udders of cows and called cowpox were protected thereafter from attacks of smallpox. He added that this tradition interested him very much and that he intended to think about it. "Don't think," wrote Hunter to him, in return; "make observations, investigate for yourself the truth of the tradition." Jenner did so, and the result is now known to all.

      These letters from Hunter contained many other interesting suggestions. For instance, it was under Hunter's direction that Jenner succeeded in finding out that in hibernating animals the temperature is very much reduced and the respirations are very slow, while the rate and force of the pulse are often so much diminished as to be scarcely more than noticeable at the extremities. Between Hunter and Jenner it had already been discovered that the sap in trees will not freeze at temperatures much lower than that at which the same fluid freezes when withdrawn from the tree, and the same thing seemed to be true with regard to the blood of hibernating animals. He learned that notwithstanding the low temperature to which it is reduced the animals are not affected particularly by the cold, though their store of fat is consumed and they awake very hungry in the spring-time.

      Besides hibernation Jenner also investigated the habits of the cuckoo, that crux of the biologist which insists on foisting its eggs upon other birds and allowing its orphan young to be brought up in alien nests, while the real young of the deceived foster-parents are often pushed out of their nests by this burly intruder which grows so fast and strong. It is needless to say, this subject interested John Hunter very much and there are a number of letters which passed between them on the subject.

      It must not be supposed, however, that young Jenner was entirely occupied with his scientific work to the exclusion of social life and recreation. He was one of the best-known men of the county, and was looked upon as a genial companion from whom might be expected on almost any occasion pleasant jests and epigrams, not too biting, with regard to friends and acquaintances. Some of these have been preserved and we quote several of them as indicative of his special vein of humor.

ON THE DEATH OF A MISER

      "Tom at last has laid by his old niggardly forms,

      And now gives good dinners; to whom pray?–the worms."

ON LORD BERKELEY'S HUNTSMAN, WHO DIED IN THE CHASE

      "Determined much higher to hoist up his name,

      Than Nimrod the hunter, in annals of fame,

      'Hark forward!' cried Charles, and gallantly whirled

      His high-mettled steed o'er the gates of the world."

DEATH AND MR. PEACH  A Short Dialogue. N. B.–Mr. P. died in April

          "P.–Awhile forbear thy horrid gripe,

            Do pray, dread Sir! remember

          Peaches are never fairly ripe

            'Till August or September."

          "D.–To gratify my longing taste,

             And make thy flavour fine,

           I had thee in a hot-house placed,

             And moistened well with wine."

      "Mr. Peach had shortened his life by the too free use of the bottle."

      We have said that Dr. Jenner's supreme accomplishment in science was the working out of the vaccination problem to a great humane conclusion. His discovery was no mere accident, nor chance confirmation of a medical tradition. He devoted himself for many years to the study of cowpox, as he had the opportunity to see it, and it is what we know of this investigation, his patience and care in eliminating all the factors of error, that stamped Jenner as a medical scientist worthy of honor. When he began practice in Berkeley, he made many inquiries among his professional brethren, with regard to their opinion of the protecting power of cowpox, but most of them had either paid no attention to such reports, or shook their heads at once, and said they were at most popular traditions, due merely to coincidences and unsupported by any credible evidence. In the face of this, Jenner began to follow John Hunter's advice to investigate. The first careful investigation dates from about 1775, and it took him more than five years to clear away the difficulties surrounding the solution of the question, in which he was interested.

      As Pasteur found in the next century, when investigating the silkworm disease, Jenner soon learned that there was more than one disease called cowpox, and that the confusion consequent upon the existence of at least two specific diseases and a number of skin affections of the hands of various kinds, which existed among dairy workers, made the recognition of the protective power of true cowpox extremely difficult. After he had differentiated genuine cowpox, however, there was no difficulty in tracing its apparent protective power. He soon found, however, that the protection was not afforded unless the cowpox had been communicated at a particular stage of the disease. In other words, after the true vaccinia has run its course, secondary affections of the skin of the cows usually take place, and if dairy workers became infected from these lesions, then no protection against smallpox is afforded them. Another important observation that Jenner made at this time was that the disease known as grease in horses is the same affection as cowpox, and that both of these diseases are smallpox as modified by the organism in which they develop. It may be said at once that this opinion so difficult to arrive at, more than a century ago, when so little was known of comparative pathology, is held at the present day, and was confirmed by the last series of investigations made under the auspices of the Jenner Society, in England.

      One difficulty that confronted Jenner in his researches was the fact that cowpox was scarce in his part of the country, and he had no opportunity of making inoculations with the disease in a proper stage, so as to put his suspicions to an absolute test. He collected much information, however, and stimulated others to the making of observations, so that when his discovery was announced the mind of the medical profession was more ready to receive it. In 1788 he carried a carefully made drawing of a case of cowpox as it occurred on the hands of a Gloucester milkmaid to London, and showed it to a number of medical men, whose opinions he wished to obtain. Among these was Sir Edward Holme, who agreed that there was a distinct similarity between it and certain stages of smallpox and considered that the question of a connection between the two diseases was an interesting and curious subject. He did not share any of Jenner's views, however, with regard to the practical importance of his discovery in this matter, and gave little encouragement to the idea that a possible prophylactic for smallpox might be discovered.

      Something of Jenner's enthusiasm for experiment may be gathered from the fact that he did not hesitate even to inject various materials related to cowpox into the arm of his own children. We know Mrs. Jenner to have been a very wonderful woman, quite as deeply interested as the doctor himself in securing the great benefit to humanity that would result from the demonstration that cowpox protected against smallpox, but it is a little bit difficult for us in these days to understand how her mother-heart could have permitted some of the experiments which Dr. Jenner's biographer, Dr. Baron, describes. 1

      The subject is indeed so surprising that I prefer to quote the passage with regard to these experiments directly from Dr. Baron:

      "In November, 1789, he inoculated his eldest son Edward, who was then about one year and a half old, with swine-pox matter. The progress of the disease seemed similar to that which arises from the insertion of true smallpox matter when the disease is very slight. He sickened on the eighth day: a few pustules appeared; they were late and slow in their progress, and small. Variolous matter (this would mean material from a smallpox patient calculated to give that disease) was carefully inserted into his arms at five or six different periods, subsequently without the slightest inflammation being excited in the part.

      "On Thursday, April 7th, 1791, variolous matter was again inserted by two small incisions through the cutis, [beneath the skin]. Then the following notes of observed conditions day after day are made: 9th, Evidently inflamed. 10th, An efflorescence of the size of a shilling

1

The life of Edward Jenner, M.D., F.R.S., Physician Extraordinary to His Majesty Geo. IV, Foreign Associate of the National Institute of France, &c. &c. &c. With illustrations of his doctrines, and selections from his Correspondence by John Baron, M.D., F.R.S., Late Senior Physician to the General Infirmary, Consulting Physician to the Lunatic Asylum at Gloucester, and Fellow of the Royal Medical and Chirurgical Society of London. In two Volumes. London: Henry Colburn, 1838.