Journal of General Microbiology (1972), 73, 1-11

Printed in Great Britain

Pneumococcal Transformation—A Backward View

Fourth Griffith Memorial Lecture

By A. W. DOWNIE

Department of Medical Microbiology,
University of Liverpool

(Delivered at the General Meeting of the Society for
General Microbiology on 11 April 1972)

Professor C. M. MacLeod, President of the Oklahoma Medical Research
Foundation, Oklahoma, U.S.A., who had agreed to give the 1972 Griffith
Memorial Lecture, died on 12 February, 1972. No text of his lecture was
available. Professor A. W. Downie generously agreed, at short notice, to
give the lecture which follows, and which uses Professor MacLeod’s intended
title.

Professor Colin MacLeod who was to have given this memorial Fred Griffith lecture
had very obvious qualifications for his selection. He had worked in Avery’s laboratory at
the Rockefeller Institute for Medical Research for eight years and was joint author of the
original paper in which it was shown that DNA was responsible for transformation of
pneumococcal types. the phenomenon first described by Griffith. Moreover he continued
and extended the work on transformation for some years afterwards at the New York
University College of Medicine where he had been appointed Professor of Bacteriology at
the early age of 32. I cannot pretend to have the knowledge and experience of MacLeod
in this field, but, because I knew personally the workers concerned in at least the early
stages of the transformation story. I decided to talk on the subject that Dr MacLeod had
chosen — although the view that I shall present is likely to be more backward than he had
intended. Then I had not recently read the first and third Griffith memorial lectures by
Professor Hayes (1966) and Professor Pollock (1970). Professor Hayes interpreted Griffith’s
experiments in terms of present knowledge of bacterial genetics and Professor Pollock's
scholarly history of the discovery of DNA emphasized the significance of the work on
transformation for the development of molecular biology. I shall not attempt a discourse
on such a high scientific level.

A few days ago I received some notes from Mrs MacLeod which showed that Colin
MacLeod had intended to describe in detail the laborious work by Avery, himself and
McCarty lasting over several years, which finally led to the conclusion that DNA was the
transforming principle which conveyed the inheritable characters of one pneumococcal
type to another. This would have been an account of absorbing interest which McCarty
may one day relate, But because of lack of inside information I cannot foilow this line.
Instead I propose to say something about the way Fred Griffith’s work on transformation
arose out of his predominant interest in bacterial typing in relation to epidemiology, and
then to say something of Avery, whose life-long interest in the pneumococcus made possible
the elaboration of Griffith’s discovery, and for whose work Griffith had the greatest
admiration.

 

Vol. 72, No. 3, was issued 24 October 1972
2 A. W. DOWNIE

Fred Griffith was born in Cheshire. After a distinguished undergraduate career he
graduated in medicine at Liverpool in 1901. He had a fellowship in the Department of
Pathology and then, after some work on the tubercle bacillus with his brother A. S.
Griffith, he joined the staff of the Local Government Board. When the Local Government
Board laboratories were taken over by the Ministry of Health during the First World War,
Griffith and Scott moved to Dudley House in Endell Street. There the Pathological Labora-
tory of the Ministry of Health functioned until the outbreak of World War IL, when its
functions were taken over and expanded into the Emergency Public Health Laboratory
Service (E.P.H.L.S.). When I first visited the laboratories in the early 1930s they consisted
of one office, a reasonably large laboratory which Griffith shared with Scott, and a media
kitchen where two technicians worked. The lower two floors of Dudley House were occupied
by the Post Office. Griffith and Scott did all their own bench work with very little up-to-date
equipment even for that period. Nevertheless excellent work was done, and both Griffith
and Scott gave endless help to bacteriologists investigating infectious disease in various
parts of the country. As Hedley Wright (1941) wrote of them, ‘A foreigner, visiting for
the first time the Jaboratory of the Ministry of Health in London, must have been little
short of appalled to ser how meanly this fundamental activity of a wealthy country was
housed and must have wondered how, thus cabined and confined, these two world-famed
workers managed to exist, let alone function, in such a chaotic environment. But he would
not be Jong there before he knew that they did so because they were Scott and Griffith,
who could do more with a kerosene tin and a primus stove than most men could do with a
Palace.” They shared the same laboratory for most of their working lives and with Allison,
who joined them in the early ’30s, they formed the nucleus of staff around which the
E.P.H.L.S. was built. They died together when Griffith’s London flat, where Scott was
staying at the time. received a direct hit during an air raid in February 1941, a few weeks
after Scott had succeeded Topley as Director of the Emergency Public Health Laboratory
Service.

Griffith’s main scientific interests were related to the epidemiology of infectious disease.
He felt that more had to be done to identify conclusively the types and the species of
bacteria found in various outbreaks, if their epidemiology was to be understood and
effective control measures taken. Hence his interest in the typing of tubercle bacilli,
meningococci, pneumococci and streptococci. The discovery of immunologically distinct
types of pneumococci was made by Neufeld & Handel (1909, 1912). Like other bacterio-
logists earlier this century —long before sulphonamides or antibiotics were discovered —
they made attempts to prepare immune sera which might be of value in treating severe
infections such as lobar pneumonia, a more common and more dreaded disease then than
it is today. The serum first prepared by Neufeld and Handel would protect mice against
some strains of pneumococci from pneumonia cases but not others, and they found that
there were at least three immunological types. These results were confirmed by Dochez and
Gillespie in 1913; and in the Rockefeller monograph published in 1917 by Avery, Chickering,
Cole and Dochez the examination of strains from cases of pneumonia led to the definition
of types I, If and HI with a heterogeneous Group IV. Griffith in 1922 found roughly the
same distribution of types of pneumococci in pneumonia cases in London, as the American
workers had noted in New York. Among the Group IV strains Griffith established that
there were 12 new serological types and certainly many more; for, of 77 group IV London
strains examined, 28 remained which did not fall within the 12 new types. However, the
finding of Group IV strains of low virulence from individual patients, usually during
convalescence, suggested to Griffith that either (a) the virulent type I, If or III strains
Preuniococcal transformation 3

might simply have been replaced by an avirulent strain as might be found in normal persons,
or (b) the immune response of the host had degraded the virulent strains into untypable
variants. This latter possibility set Griffith working with rough non-capsulated avirulent
pneumococci. These he had produced in the laboratory by growing smooth virulent type
I, I] or UI strains in the presence of homologous type antiserum, a technique which had
been used by Stryker in Avery’s laboratory some years before (Stryker, 1916). The possi-
bility of acquisition of virulence by these experimentally produced rough forms, and the
possible reversion to virulence of weakly virulent strains found in the throats of conva-
lescent patients and healthy persons, prompted the experiments which resulted in the
discovery of transformation of types. The subcutaneous injection of large doses of rough
pneumococci into mice occasionally led to fatal infections from which smooth virulent
pneumoccoci of the original type were isolated. Reversion to virulence could be achieved
more readily if rough pneumococci, derived from type II, were injected together with a
large dose of heat-killed organisms of smooth virulent type I. The most surprising result,
however, came from Griffith’s control experiment, where heat-killed smooth organisms
from type I were injected along with rough organisms derived from type I]. The mice died
of generalized infection with virulent type I pneumococci: an apparent transformation of
pneumococcal type. Grifhth found this result, an example of pure serendipity as Pollock
pointed out, difficult to believe, and as his paper of 1928, republished in the Journal of
Hygiene in 1966, shows, he made many experiments with extensive controls to establish
this surprising transformation of one pneumococcal type into another. Because Griflith
was conditioned to believe that bacteria existed in immutable types, offering a solid basis
for epidemiological investigation, one can imagine he was at first loath to accept his own
results. Fred Griffith was a very shy person, rarely went to meetings and could not readily
be persuaded to read a paper. | think it is safe to say that if he had been persuaded to
communicate his findings to the Pathological Society - there was no Society of Genera!
Microbiology then —those who knew Griflith’s work would have found his results sur-
prising, but would have accepted them. It was a long time after his experiments were
completed before the results were published, and by then he had started his studies on
streptococcal infection. According to Scott, Neufeld had visited their laboratory and had
been told of Griffith’s transformation experiments. Some months after he had returned to
Berlin, Neufeld wrote to ask Griffith when the results were to be published. as he, Neufeld,
had confirmed Griflith’s results and wished to write them up. This explains why Neufeld
and Levinthal’s confirmatory paper appeared so soon after Griffith’s; and indeed, in
Neufeld’s paper it is stated that one of the authors had visited Griffith’s laboratcry some
months before, and been told of Griffith’s results and the technique used (Neufeld &
Levinthal, 1928).

Most of the subsequent work on transformation was done in Avery’s laboratory at the
Rockefeller Hospital in New York, which had been the centre of pneumococcus research
in America for the previous fifteen years. But the initial confirmatory experiments were
not made by Avery, who for many months refused to accept the validity of transformation
and was inclined to regard the finding as due to inadequate experimental controls! This
scepticism was understandable in one who had devoted so much effort and skill to the
doctrine of immunological specificity. But Avery was suffering at that time from thyrotoxi-
cosis and left the laboratory for some months. During that time his colleague Dawson not
only confirmed Griffith’s findings, but went further and showed that transformation of
type II to type I] could be effected i vitro by incubating a very small inoculum of living
R cells, derived from type H, together with anti-R serum and a concentrated suspension
4 A. W. DOWNIE

of heat-killed virulent type III (Dawson & Sia, 1931). He confirmed Griffith’s observation
that transformation did not occur if the smooth type II suspension was heated above 80 °C.
He further found that heat-killed preparations from old cultures were useless, and that
freezing and thawing of previously effective preparations destrayed the transforming prin-
ciple (Sia & Dawson, 1931). He suggested that the essential factor was destroyed by
bacterial enzymes. Pure S.S.S. - that is, type-specific capsular polysaccharide from type III
- failed to transform rough forms derived from type JI. Later he found that even smooth
type II could be transformed into type II, apparently without the intermediary of rough
forms (Dawson & Warbasse, 1931). The next step was taken by Alloway, also working in
Avery’s laboratory (Alloway, 1932, 1933). He found that transformation could be achieved
by bacteria-free extracts alone prepared from young cultures of virulent pneumococci.
The sedimented bacteria were dissolved by sodium desoxycholate and heated at 60°C
for 10 minutes. The extracts could be filtered through Berkefeld candles, and absorbed
with charcoal, without losing activity. The transforming principle could be precipitated by
10 vol. of alcohol or acetone. The activity of the final preparation was such that 0-05 ml
of extract (50 ml concentrated from 5 | of culture) was sufficient to produce transformation
of R forms in the presence of serum or serous fluid. These extracts contained specific
polysaccharide in sufficient concentration to induce active immunity in mice. However,
Alloway did not think that specific polysaccharide was the transforming principle and
concluded that ‘if $.5.S. is involved it is present in a different physical state, or in com-
bination with some other substance which confers on it properties not found in the purified
substance’.

No further significant paper on transformation appeared until the famous paper in 1944
by Avery. MacLeod and McCarty. But this paper was the result of several years’ labour,
as 1s obvious from the paper itself and from the letter. quoted by Pollock, written by Avery
to his brother Roy in 1943. In 1933 Alloway left Avery’s laboratory and Dawson had by
then gone to the Presbyterian Hospital in New York. Neither apparently continued the
work on the transforming principle. At this stage nothing was definitely known about the
nature of the active substance. Was it S.S.S. combined perhaps with some other substance
as Alloway had suggested, was it protein, or was it something else?

When MacLeod came to Avery’s laboratory as a junior member of staff in 1934 he took
up the study where Alloway left off in 1933. From the start he had difficulty in obtaining
regularly active extracts, and it took another three years to work out the conditions necessary
for constantly reproducible results. Not all rough strains of pneumococci were suitable for
transformation — we would use the term “competent’ today. This difficulty was overcome
by transferring a smooth type II through 36 cultures in the presence of type II serum and
plating out the 36th subculture. Amongst the rough single colony isolates one — R36A —
gave a high and consistent yield of transformants in the presence of heat-killed type III
cells. and was used in all subsequent work. When it came to preparing active transforming
extracts from virulent type IIE pneumococci, unexpected difficulties were met. Not all
batches of broth proved suitable, but it was found that absorption of the broth with charcoal
made most samples satisfactory. Enzymes from the extracted pneumococci slowly destroyed
the transforming principle, and some samples of serum added to the reaction mixture had
the same effect. These difficulties were overcome by heating the pneumococcal suspension
before extraction, and the serum, to 60 °C for 30 minutes. The active principle had been
found by Alloway to be precipitated by alcohol, and this step was regularly adopted because
stability was thereby improved. Not until 1937 could active transforming extracts be con-
sistently prepared and a method of titrating this activity be developed. Then the work on
Pneumococcal transformation 5

purification began, for up to this point the transforming extracts contained, among other
things, pneumococcal protein, non-specific polysaccharide (C substance) and type-specific
capsular polysaccharide. The protein could be removed by Sevag’s method of repeated
shaking with chloroform without affecting the concentration of transforming principle.
The type III specific polysaccharide could be removed by digestion with Dubos’s specific
enzyme, which I will mention later. The active principle could be separated out from the
resulting fluid by careful addition of alcohol, and was further purified by repeated solution
and reprecipitation. By chemical analysis, by its ultraviolet absorption curve and its
behaviour with various enzymes in comparison with a pure preparation of desoxyribo-
nucleic acid, the active principle was identified as DNA. The authors, however, were guarded
in their summary and conclusions: for example: ‘Evidence is presented, that the chemically
induced alterations in cellular structure and function are predictable, type specific and
transmissible in series’; and ‘The evidence presented supports the belief that a nucleic
acid of the desoxyribose type is the fundamental unit of the transforming principle of
Pneumococcus type HII’. :

Avery published only two further papers on the nature of the transforming principle,
both with McCarty (McCarty & Avery, 1946). McCarty had prepared a relatively pure
desoxyribonuclease from ox pancreas and, with Avery, showed that this enzyme destroyed
the transforming activity of the active principle under the same conditions that it broke
down purified DNA from calf thymus. In the second paper McCarty and A ‘ery showed
that much higher yields of the transforming principle could be obtained by the use of
citrate in the presence of magnesium salts to inactivate DNase in the pneumococcal sus-
pension from which the transforming principle was to be prepared. These papers merely
strengthened the case for DNA being the active principle. and met the objections of those
who suggested that some protein contaminant was responsible for transformation, rather
than DNA itself. Later Hotchkiss. who had come to Avery’s department in 1937 and
continued to work there after Avery left in 1947, provided further chemical evidence that
the preparations of DNA responsible for transformation contained no contaminating
protein. Although Avery himself never in print identified DNA as the essential genetic
material of the pneumococcal cell. his pupils were more committed. In a paper published
in 1949 on pneumococcal transformation Harriet Taylor (later H. Ephussi-Taylor), who
was working in Avery’s laboratory, wrote: “It appears justified therefore to visualize the
transforming principle much as the geneticist pictures genes’ (Taylor, 1949).

McCarty turned to the study of streptococci soon after the two publications with Avery
in 1946; but MacLeod, who had moved to University College of Medicine, New York.
in the early 1940s continued work on pneumococcal transformation. In transformation
experiments, Austrian and MacLeod showed that the type-specific M protein of pneumo-
coccus, which they had discovered, could be transferred independently of the specific cap-
sular polysaccharide (Austrian & MacLeod, 1949a, >). They made the important suggestion
that transforming extracts of encapsulated pneumococci contained a multiplicity of
deoxyribonucleic acids which controlled the specificity of the several cell characters des-
cribed. In a paper published in 1950 with Krauss, MacLeod found that among experi-
mentally transformed pneumococci derived from various serological types, the amount of
8.8.8. formed and the virulence of the strain was controlled by the genetic apparatus of the
donor strain (MacLeod & Krauss, 1950). During the next few years MacLeod extended
the study of transformation reactions to streptococci. In an examination of streptococci
from various Lancefield Groups and of viridans strains, he found two strains of viridans
streptococci which could be transformed to streptomycin resistance by DNA-containing
6 A. W. DOWNIE

extracts from a streptomycin-resistant pneumoccocus. Conversely, streptomycin-resistant
variants of these two strains of streptococci were able to confer this property to a sensitive
pneumococcus. Resistance to optochin could be transferred by naturally resistant strepto-
cocci to the naturally sensitive pneumococcus. The two strains of viridans streptococci
were more efficient receptors of pneumococcal transforming principle than were pneumo-
cocci, and it was concluded that efficiency of transformation did not necessarily indicate
closeness of relationship (Braco, Krauss. Roe & MacLeod, 1957). In further transformation
reactions between these two streptococcal strains and a rough pneumococcus, using strepto-

nycin resistance as a marker, he found that the receptor strain was more easily transformed
when the donor strain was, itself, a transformant which had received DNA from the
recipient species (Krauss & MacLeod, 1963). MacLeod’s participation in the original
discovery of DNA as the transforming principle, and his continued interest in bacterial
genetics, explains the tile that he had chosen for this memorial lecture.

To go back a little to the discovery of DNA as the transforming principle: it seems, as
has been emphasized by Pollock and more recently by Wyatt (1972), that the fundamental
importance of Avery’s work was not generally appreciated for several years, perhaps not
until Hershey and Chase’s work with bacteriophage in 1953. But although Avery and his
colleagues were rather careful in the conclusions in their paper. and left their options open,
they clearly realized the significance of DNA as the genetic material of the bacterial cell.
Sir Henry Dale, in his presidential address to the Royal Society in 1946, announced the
award of the Copley Medal to Avery. Referring to the transformation paper of 1944 he
said: “Here surely is a change to which. if we were dealing with higher organisms, we
should accord the status of a genetic variation; and the substance inducing it — the gene
in solution, one is tempted to call it — appears io be a nucleic acid of the desoxyribose
type’. Burnet visited Avery in December 1943, just after the paper had gone to press, and
heard at first hand the latest results on the transformation story. In a letter to his wife at
this time he wrote: ‘Avery has just made an extremely exciting discovery which, put rather
crudely, is nothing less than the isolation of a pure gene in the form of desoxvribonucleic
acid". This was probably Avery’s interpretation of his own work. Burnet goes on to com-
ment, writing in 1968: ‘nothing since has diminished the significance or importance of
Avery’s wor’.

Avery and Griffith were in many ways rather similar characters. Both were confirmed
bachelors. ‘Both were extremely modest, meticulously careful in their experimental work
and extremely generous with time spent helping others. Both were almost excessively
cautious in reaching conclusions, and both made major contributions to knowledge
relatively late in life’ (Pollock, 1970). He might have added that both had brothers who
were eminent bacteriologists and both had one particularly close friend throughout their
working lives — Griffith had Scott and Avery had Dochez. But there was one great difference
i their working conditions. Griffith was always a lone worker — perhaps only partly
because funds were not available to pay for assistants. On the other hand, Avery, in the
Rockefeller Hospital, always worked with a team and could, when necessary, enlist the
assistance of those whose special knowledge or skills would help to solve the problems
which then occupied his attention. For, although he was rather shy and avoided speaking at
meetings whenever he could, in private conversations his enthusiasm for his work could be
presented with dramatic force and persuasive eloquence.

In 1913 Avery was asked by Rufus Cole, then director of the hospital, to join the group
working on lobar pneumonia. Dochez & Gillespie (1913) had just confirmed Neufeld’s
observations on the multiplicity of serological types of pneumococci. With Avery’s arrival
Preuniccoceal transformation 7

at the hospital there began a collaboration with Dochez which persisted in an informal
but highly creative form for years after Dochez left the Rockefeller Institute, to become a
professor of medicine at Columbia. As Dubos wrote: ‘The two men shared a bachelor’s
apartment for many years and apparently never tired of discussing, night after night,
problems of aetiology and pathogenesis, It would demand much psychological perspicacity
to delineate the contributions of each participant in these midnight dialogues which had
so much influence on the evolution of medical microbiology’ (Dubos, 1956). Avery’s work
with the Rockefeller team began with the study of pneumonia patients and the strains of
pneumococci isolated from them. In 1917 Dochez and Avery published their first paper
on the type-specific soluble substance (S.S.S.) of pneumococcus (Dochez & Avery, 1917).
This substance appeared after a few hours in pneumococcal cultures. $.S.S., of the type
corresponding to the infecting organisms, was detected in the urine and blood of a pro-
portion of pneumonia patients, and its presence in the blood was a bad prognostic sign,
since most of these patients died. It was to determine the chemical nature of S.S.S. that
Avery persuaded Michael Heidelberger to join his department. Their work led to the iso-
lation and characterization of the specific capsular polysaccharides of the first three types
of pneumococci (Heidelberger & Avery, 1923, 1924; Heidelberger, Goebel & Avery, 1925).
The purified preparations, first made, were non-antigenic when inoculated into rabbits,
and were regarded as haptenes. But it was shown by Schiemann and his colleagues (1927,
1931) that active immunity to infection could be induced in mice by the injection of very
small doses ~ concentrations below that which would precipitate with the cUcresponding
type-specific serum ~ while larger doses had no immunizing effect. Indeed, large doses
produce the state of specific immunological paralysis. The earlier preparations had been
made from suspensions of pneumococci from young cultures, or from the fluid from
eight-day cultures; their isolation had involved heating to 100 °C and the use of strong
acid and alkali. Less drastic treatment subsequently yielded from cultures of type I better
preparations - the acetylated form — which, in a dilution of 1 in several million, would
immunize mice and which would absorb all antibodies, including protective antibodies,
from type I immune serum (Avery & Goebel, 1933). Francis and Tillett, in Avery’s depart-
ment, showed that the specific polysaccharides were antigenic on intradermal injection
into man and that the deacetylated product would also induce the formation of mouse-
protective antibodies in normal persons (Francis & Tillett, 1930; Francis, 193.4). This
finding later led to the use of purified specific polysaccharides in place of whole pneumococcal
vaccines in prophylactic immunization of susceptible populations against pneumococcal
infections. MacLeod was actively concerned with such prophylactic triais in military
populations during the war.

By 1930 it had been established, largely through the work of Avery and his group, that
the virulence of pneumococci was dependent on the capsular polysaccharide and that
immunity, type-specific in character, was dependent on antibodies to it. It occurred to
Avery that, if some means could be found of breaking down the capsular polysaccharide
of infecting pneumococci in the animal body, the offensive mechanism of the organism
would be lost and the animal might be cured. He thought that in soil, where complex
carbohydrates must be broken down in the decay of vegetable matter, micro-organisms
might exist which would break down the specific pneumococcal polysaccharides. At this
time Dubos, who had been working in Waksman’s laboratory in New Jersey, came to visit
Avery. When Avery learnt that Dubos had been interested in soil microbiology, he imme-
diately enlisted his assistance to tackle the problem he had in mind. A medium containing
only ammonium sulphate, dibasic potassium phosphate and tvpe III capsular polysac-
8 A. W. DOWNIE

charide was used. Bacteria from samples of soil served as inoculum. Decomposition of the
polysaccharide in the medium was tested at intervals by precipitation tests with type LI
antiserum. From one soil sample the bacteria were found to break down the polysaccharide.
After months of subculture and purification by dilution, this decomposition was found to
be due to an aerobic Gram-negative sporing bacillus. Filtrates of cultures of this organism
were highly specific for type II] polysaccharide and had no effect on polysaccharides from
other pneumococci (Dubos & Avery. 1931). Enzyme preparations were found capable of
curing mice infected with type III pneumococci (Avery & Dubos, 1931). rabbits infected
intradermally with a virulent type LW pneumococcus (Goodner, Dubos & Avery, 1932)
and, finally. had a curative effect on pneumococcus type IIT pneumonia in cynomolgus
monkeys (Francis. Terrell, Dubos & Avery, 1934). The potency of different lots of the
enzyme varied, but even after more purified preparations were obtained (Dubos, 1935)
Avery was cautious — his younger assistants thought too cautious — about testing the value
of the enzyme preparations on type III pneumonia in man. The discovery of sulphonamides
at this time obviated the need for such tests, and satisfactory trials of the enzyme were
never made in pneumonia patients. Thus a brilliant idea, which led to a great deal of
interesting and successful experiment, never led to the clinical application which had been
hoped for.

The discovery of the biological specificity and antigenicity of the pneumococcal capsular
polysaccharides by Avery and his colleagues came at a time when it was generally con-
sidered that such specificity was attributable only to proteins. Following the lead given by
the work of Avery. specific serological reactivity was later shown to be due to polysaccharides
in other bacterial groups-—the tubercle bacillus, Friedlander’s bacillus, Haemophilus
iifluenzae, Salmonella and other organisms. Avery’s group showed that there was serological
cross-reactivity between polysaccharides trom type If pneumoccoci, from a strain of
Friedlander’s bacillus (Avery, Heidelberger & Goebel, 1925) and from gum arabic (Heidel-
berger. Avery & Goebel, 1929). These cross-reactions were in part explained by the studies
of Avery and Goebel, published in eight papers between 1929 and 1934, on conjugated
carbohydrate-proteins. These showed that the fundamental specificity of sugar residues was

ependent on configuration, size and nature. This work provided one of the foundation
stones for tue science of Immunochemistry.

In addition to the work I have touched upon, many other papers dealing with bacterial
growth and lysis and C reactive protein came from Avery’s laboratory. Many of these
papers were published by Avery’s colleagues alone, for he would never allow his name on
a paper unless he had personally done a considerable proportion of the work involved.
For example, of 61 papers from his department from 1930 to 1934 inclusive, only 14 bore
Avery’s name. For at least fifteen years Avery supervised and guided the work of Lancefield
on the antigenic structure of streptococci. He was co-author of only the first two papers,
one of which in 1919 demonstrated that there were different immunological types of
haemolytic streptococci (Dechez, Avery & Lancefield, 1919).

The quality of Avery’s scientific contributions was recognized by his election as a
Foreign Member of the Royal Society, just before the paper on DNA and the transforming
principle was published. The award of the Copley medal in 1945, the highest distinction
the Royal Society could confer, was made in recognition of the importance of that discovery.

Burnet records of his meeting with Avery in 1943: ‘Avery was an oldish man then,
beginning to live a little in the past, and happy to relate to interested visitors how his work
with the pneumococcus had reached this climax’. Burnet did not realize that for many
years Avery had been putting on this carefully rehearsed performance for the benefit of
Preumococeal transformation 9

visitors and new members of staff. It was an exciting and absorbing story which lost
nothing in the telling. For new assistants it was valuable as the background into which
they could fit according to their inclinations or special skills.

For an insight into Avery’s personality it is worth reading part of the speech he made
when presenting the Kober Medal of the American Association of Physicians to Dochez
in 1949. This was quoted by MacLeod when he wrote Avery’s obituary (MacLeod. 1957).
‘Throughout his studies there is unique continuity of thought centering in the dominant
problem of acute respiratory diseases. The results of his work are not random products of
chance observations. They are the fruits of years of wise reflection, objective thinking and
thoughtful experimentation. I have never seen his laboratory desk piled high with Petri
dishes and bristling with test tubes, like a forest wherein the trail ends and the searcher
becomes lost in dense thickets of confused thought. I have never seen him so busy taking
something out of one tube and putting it into another there was no time to think of why
he was doing it or what he was actually looking for. I have never known him to engage in
purposeless rivalries or competitive research. But often I have seen him sit calmly by, lost
in thought while all around him others with great show of activity were flitting about like
particles in Brownian motion; then, | have watched him rouse himself, saunter to his desk,
assemble a few pipettes, borrow a few tubes of media, perhaps a jar of mice, and then do
a simple experiment which answered the very question he had been thinking about, when
others thought he had been idling in aimless leisure.” MacLeod adds that this paragraph
epitomizes Avery’s own approach to investigation and his philosophy of the “true inward-
ness of research’. Another colleague. Dubos, wrote in 1956: ‘That he was not made a
Nobel Laureate remains to this day a matter of painful surprise in many scientific circles,
since all his discoveries had an obvious quality of perfection and finality, immediate useful
application, and great influence in moulding the activities of other investigators. One
might hope that the Nobel Academy will some day acknowledge this oversight and publicly
recognize as once the Académie Frangaise did for Moliere

Rien ne manquait a sa gloire
Il manquait 4 la notre’.

If I have seemed to devote an unduly Jarge part of this address to Avery and his work.
it is because I shared with Colin MacLeod a great regard and respect for Avery as a man
and as a scientist. And I feel that Fred Griffith would not have begrudged this small tribute
to one who had brought to such a successful conclusion the story which he so dramatically
began.

REFERENCES

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