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Early Contributors to Nephrology
Am J Nephrol 1994;14:371-376
Department of Medicine, University
College London Medical School,
London. UK
John Blackall (1771-1860):
Failure to See the Obvious in
Dropsical Patients with
Coagulable Urine?
Key Words
Renal pathology
Mercury poisoning
Despite his success in publishing a book which was widely read and which
drew attention to the fact that some cases of dropsy are associated with coagu­
lable urine, John Blackall failed to make the link between this phenomenon
and disease of the kidneys. Thus, to Richard Bright must go the credit for
providing the critical understanding of the phenomenon. The single most
probable reason for Bright’s success and Blackall’s failure was that Bright car­
ried out post mortem examinations of almost all of his patients. In addition,
Bright was ruthlessly systematic in documenting his autopsy findings, and not
least was the fact that he possessed the rare talent of being objective in looking
at his data, without being influenced by the preconceptions of the times.
Identification of the cause of dropsy, i.e. the accumula­
tion of fluid in the serous cavities and in the interstitia of
tissues, intrigued virtually all of the ancient and medieval
medical writers. A careful search of the writings on dropsy
of such luminaries as Hippocrates, Galen, Areteus, Aetius
and Avicenna reveals sporadic case reports of hardened or
scirrhous kidneys or kidneys which are altered from their
normal appearances [I], A diminution of the volume of
the urine was similarly recognized. Similar reports are
scattered throughout the literature of the 17th and 18th
centuries and these have been elegantly catalogued by
Rayer [2], It is clear, however, that by the beginning of the
19th century it had not been realized that there could be a
causal relationship between kidney disease and dropsy.
Perhaps the single most important reason for this was the
scarcity of post mortem examinations of the internal
In 1790 Cotugno ushered in an innovative experimen­
tal approach to dropsy; he examined the urine of dropsical
subjects and found that in some it coagulated on heating
[3]. Others had shown that blood and serum may be
present in the urine following scarlatina, but this was
regarded as a form of bleeding into the urine. Noting that
normal serous fluids did not coagulate on heating, Cotu­
gno found that they did if the serous membranes were
inflamed. Extending this principle he performed an ex­
periment to test whether the dropsical fluid was excreted
into the urine:
‘It seemed best to settle this question by a definite experiment,
heating the urine. For I had often conclusively shown that the
fluid collected beneath the skin of such dropsical cadavers con-
Leon G. Fine, FRCP
Department of Medicine
University College London Medical School
5 University Street
London W CIE 6JJ (UK)
© 1994 S. Karger AG. Base!
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Leon G. Fine
Jennifer A. English
tained material capable of coagulation and I hoped that, if the sick
man passed such fluid by way of the urine, coagulation would be
seen if the material which flowed out were heated, which, as I had
anticipated, was proved by experiment. For with two pints of this
urine exposed to the fire, when scarcely half evaporated, the
remainder made a white mass already loosely coagulated like egg
Thus it was shown for the first time that urine, which is
never coagulable in healthy people, can under some cir­
cumstances contain a coagulable substance.
Cotugno also found coagulable material in the urine of
some diabetic subjects. He erred, however, in concluding
that the presence of coagulable material signalled recov­
ery of the disease in that it reflected passage of such co­
agulable material from the serous fluid of dropsy into the
urine. Nevertheless, this seminal work involving genuine
experimentation must be heralded as ‘one of the first
triumphs of chemistry applied to pathology’ [2],
‘... the kidnies [sic] were much harder than they usually are. The
cortical part was thickened and changed in its structure from the
deposition of coagulable lymph and there was a small quantity of pus
in the pelvis of one of them. I do not conclude, however, from these
appearances and those which were found in the former case that the
kidnies are always diseased when the urine in dropsy contains much
Thus, no relationship between kidney disease and co­
agulable urine had been established in the early 19th cen­
tury. In France, Fourcroy (1800), Nysten (1811) and Chapotain (1812) described coagulable urine in patients with
dropsy, with Nysten even noting that it: ‘foamed strongly
on shaking and remained frothy for a long time’, but none
of these authors appears to have been drawn to the kid­
neys to explain the phenomenon [2].
John Blackall and Dropsical Patients
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Fig. 1. John Blackall ( 17 7 1- 1860).
Cruikshank deserves the credit for being the first to
attempt, in 1798, to separate those dropsies in which the
urine is coagulable from those in which it is not [4], Writ­
ing in Rollo’s Cases o f Diabetes Mellitus he suggests that
the presence of coagulable material implies that the drop­
sy is dependent on ‘morbid viscera’, which at the time
meant a diseased liver or spleen. Again the kidney did not
merit a mention!
The foregoing remarks show that by the early 19th cen­
tury there was a tenuous understanding that some cases of
dropsy were associated with abnormal kidneys and that
some cases were associated with coagulable urine. What
now seems to be an obvious association, i.e. the relation­
ship between diseased kidneys and coagulable urine, was
obviously not intuitive at the time. It was arrived at, indi­
rectly, through the writings of William Wells in 1812. In
his paper to the Society for the Improvement of Medical
and Surgical Knowledge [5], he not only demonstrated
that the red colour of the urine in dropsies associated with
scarlatina was due to the red matter of the blood (red
blood corpuscles had not yet been discovered), but also
that this urine contained the serous portion of blood, i.e.
serum. Using both heat and nitric acid he showed that
fioccules appeared. To quantify the amount of serum in
the urine, he mixed different proportions of serum and
normal urine. Out of 138 cases of scarlatina he found ‘se­
rum’ in the urine of 78. Importantly, he noted that when
serum was added to urine, the urine may have a perfectly
normal appearance, and indeed he found that ‘serum’ was
present in the urine of 23 of 29 cases of dropsy not associ­
ated with scarlatina. Once again he was limited by his
inability to examine the viscera of such patients after
death. He records 1 case in which:
The P octor, in Ins obser­
vations oil this rase, is inclined to lay
m eat stress on the coagulability o f the
urine by b eat,
li e says,
“ The extraordinary coagulability
o f the urine fot ms a peculiar feature
o f the complaint. It was principally
this circum stance which determ ined
me to bleed, notw ithstanding the ap ­
parently hopeless condition of the pa­
tient and the obscurity o f the pulse as
a guide.
1 have never h esitated,
when the urine coagulates, to bleed in
dropsies, and I have never yet had
reason to believe the practice injudi­
cious ; and I cannot help expressing
here my opinion, that the profession
are highly indebted to Dr. TIi .ackam .,
for so pointedly directing onr a tte n ­
tion to this condition of th a t dis­
1 am not, Indeed, prepared to ad ­
mit, that the sensible qualities o f the
urine form a principle upon which to
found a practical division of dropsies,
hut 1 feel assured that the coagulabi­
lity of the urine w ill almost invariably
w arran t tile practice o f bloodletting.
The ap pearance of the blood draw n
incoutrovertihly proved, in this in ­
stance, the iiillanimatory tendency,
iu d the propriety of the practice."
Fig. 2. Title page of the 1st edition of John Blackall’s book on
Fig. 3. Extract from a review of the book Clinical Reports on
Dropsies by Robert Venables, which appeared in the Lancet of 18
December 1824. The recognition that was accorded to Blackall’s
work on dropsy is evident from the remarks of the reviewer.
Cure o f Dropsies
John Blackall (fig. 1) was born in 1771 in Exeter,
England, and educated at Exeter Grammar School and
Balliol College, Oxford. He received his BA degree in
1793 and his MD degree in 1797. He received a second
MD degree from St. Bartholomew’s Hospital in 1801. He
gained his MRCP in 1814 and became FRCP in 1815. He
worked as a physician in Totnes, Devon, from 1801 to
1807, after which he returned to Exeter. In 1812 he
became physician to the Hospital for Lunatics. In 1813 he
published his Observations on the Nature and Cure o f
Dropsies [6] (fig. 2) which went through 5 editions (1813,
1814,1818,1820,1824) including an American edition in
1820 based on the 3rd London edition. This work was
widely regarded as a significant contribution to the medi­
cal literature (fig. 3).
Blackall was highly regarded as a physician:
‘His information on medical matters, singularly extensive and
accurate, had been qualified by a wide and varied research from
many departments of human knowledge; his diagnostic powers were
of the highest order’ [7],
He practised until the age of 80 years and died aged 88
years in 1860.
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John Blackall and Observations on the Nature and
Urine differs
little from the healthy state
Without bloody
Related to
of mercutials
Fig. 4. Schematic overview of the catego­
ries of dropsy described by Biackall.
Blackall’s single work (no other publications by him
have been traced) has a title that raises the possibility that
he may have made the seminal discovery for which
Richard Bright later received the credit. This article
examines whether this was the case or not. His book was
fully titled Observations on the Nature and Cure o f Drop­
sies and Particularly on the Presence o f the Coagulable
Part o f the Blood in Dropsical Urine and contained 15
chapters and An Appendix Containing Several Cases o f
Angina Pectoris with Dissections, etc. Biackall indicates in
the introduction that he was aware of previous reports of
coagulable urine in dropsy and cites the writings of Fordyce, Darwin, Cotunnius (Cotugno), Vauquelan, Fourcroy and Cruikshank. His interest in the topic seems to
have been stimulated by a single case under the care of his
preceptor Dr Latham.
It is difficult to follow a simple pattern of thought
through the book, so a simple description of its contents
would be confusing. Figure 4 categorizes, in a simplified
fashion, the different forms of dropsy that Biackall con­
sidered. What follows describes his experience with each.
Dropsy in Which the Urine Differs Little from the
Healthy State
In this general category Biackall describes individual
cases of anasarca without any unique or distinguishing
features, in which the urine is described as pale, crude and
apparently diluted. He notes that this is not very common
in dropsy. In none of the patients was a coagulum pro­
duced by heat or nitrous acid but in 2 cases oxymuriate of
mercury detected a small amount of ‘albumen’. For no
obvious reason, he concludes that this form of dropsy is
connected with ‘great and irretrievable injury of internal
Urine coagulable
by heat
With blood}
Unrelated to
to medication
organs’. He regarded digitalis as being of little use in the
treatment of these patients, and indeed felt that the poly­
uria was a very bad sign as it precluded the use of many
He described another group of cases in which the only
difference seems to be that the volume of urine was small.
Here for the first time he alludes to the ‘bad effects of
mercury’, which he regarded as being far more common
than generally suspected, as is discussed below.
Dropsy in Which the Urine Is Not Coagulable.
Is Scanty. High Coloured and Deposits a Sediment
Biackall includes a variety of cases of ascites, hydrotho­
rax, pericardial effusion and anasarca in this category. He
refers to the sediment in the urine as ‘lateritious’ (brickcoloured). The sediment in many cases was pink. Of the
21 case reports provided, most are very brief and in only 2
(cases 11 and 21) were autopsies performed. In 1 case the
liver was hard and small.
Biackall attempted to define the nature of the sedi­
ment. It was precipitated by ‘the infusion of galls’ but not
nitrous acid, suggesting that it was not protein. Oxymu­
riate of mercury occasionally produced a coagulum re­
sembling the effect of heat. Biackall concluded that this
was: ‘in a great measure at least, albumen'. He further
concluded that the pinkish material was: ‘pure ammonia,
the muriate of barytes and acetate of lead [and] a large
proportion of saline matters’. Despite the fact that he paid
such attention to this pinkish sediment, he is objective
enough to conclude that it is not always present in dropsy
associated with a scirrhous liver, as Cruikshank had pro­
posed, nor did its absence allow any conclusions to be
drawn about the cause of the dropsy.
John Biackall and Dropsical Patients
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Urine not coagulable
by heat but scanty,
high coloured and deposits
a sediment
‘... the kidneys were rather soft and flaccid and more loaded with
fat than could have been suspected after so long an illness, but in
other respects quite natural.’
Of interest is the fact that this particular case, while
included in the chapter on scarlatina, did not have scarla­
tina but an erysipelatous inflammation of the lower
extremities. Couched in modern terms this case is likely
to have been secondary infection of grossly oedematous
legs, while the renal appearance is consistent with ‘lipoid
As far as the bloody urine sediment is concerned,
Blackall had no doubt that this was true haemorrhage, as
‘its appearance could hardly deceive’.
Dropsy in Which the Urine Is Coagulable by Heat:
Associated with Administration o f Mercurial
Throughout the book Blackall alludes to the potentially
deleterious effects of mercury (calomel). He seems to have
had little respect for a therapy which, if continued, led to
the gums becoming sore and greatly debilitated the pa­
tient. The refrain: ‘I cannot help fearing that mercury had
some share in thus changing the type of disease’ (chapter
4, case 8) is chanted in one form or another repeatedly.
Blackall was impressed with the long-term adverse effects
of mercurials, and when complicated by continued saliva­
tion, he believed the underlying disease to be more speedi­
ly fatal. One autopsy was performed on a patient who suc­
cumbed to general debility, severe oedema of the legs and
a sloughing ulcer of the leg. The urine was coagulable by
heat. Post mortem examination showed pleuropericarditis was present and the: ‘kidneys [were] unusually firm’.
Another autopsy was performed on a patient who re­
ceived mercurials for treatment of diarrhoea, which
turned out to be related to ileocaecal tuberculosis, and in
this case: ‘the kidneys [were] remarkably loaded with
blood as if infected’.
Dropsy in Which the Urine Is Coagulable by Heat:
Associated with Drinking Cold Water when Heated
and Fatigued. Exposure to Cold. Intemperance.
Cachexia and Scurvy
This is a heterogeneous collection of cases of anasarca,
ascites, or leg swelling in which scanty, coagulable urine
was found. No insight into involvement of the kidneys
was provided.
Dropsy in Which the Urine Is Coagulable by Ileal:
Associated with Hydrothorax, Ascites and
It is not at all clear what this group of 9 patients with
‘hydrothorax’ represents, because examination of the
chest using percussion and auscultation had not been
described. In one case the autopsy revealed a unilateral
hydrothorax, atelectasis of the underlying lung and the:
‘kidneys [were] remarkably small and sound’.
Similarly, in an autopsy on 1 case of ascites with
copious coagulable urine, a hardness and enlargement of
the right lobe of the liver was found, firmly resisting the
knife. The other viscera were sound: ‘except the kidneys,
which were remarkably solid and hard, their stmeture
somewhat confused’. Blackall recognized this appearance
of the kidneys to be very uncommon and remarks that he
is not aware that: ‘such a hardness approaching to scir­
rhous has ever been attributed to the use of mercury’, but
contradicts this statement by referring to 1 of the cases
described above.
Blackall’s Overview
In his defence it must be said that any failure of Black­
all to recognize the association of coagulable urine with
kidney disease can be attributed to the very small number
of post mortem examinations which he performed on his
patients. But he did fail to recognize the association! In
attempting to summarize his findings, he is obtuse and
vague in the extreme. Indeed, he indicates that coagulable
urine: ‘is not connected exclusively with any particular
situation’. He did attempt to address the nature of the
coagulable substance that he recognized as ‘serum’, noting
that both heat and nitrous acid produced the coagulum. It
appears that it was commmonly accepted at the time that
oxymuriate of mercury could be used to detect very min­
ute quantities of albumin, but Blackall considered this test
to be unhelpful: ‘since it acts on the urine in many other
cases of dropsy’, i.e. also those that do not have coagulable
urine. This statement confirms that he thought that the
coagulum was some component of serum other than albu­
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Dropsy in Which the Urine Is Coagulable by Heat:
Associated with Scarlatina
Blackall devotes almost 140 pages to this topic. In most
cases the dropsy appeared weeks or months after the
attack of scarlatina, and in half of these cases Blackall
found a blood-stained urine sediment. Most were treated
with digitalis; indeed, Blackall states: ‘I know of no
instance where digitalis has failed’. A few cases developed
erysipelas of a limb at the time that dropsy was present.
In only 1 case was an autopsy done and in this:
In some cases, he considered the urine to be deficient
in urea (a substance isolated in 1797 by Fourcroy and
Vauquelin [8]), acidic, ‘unanimalized’ and resistant to
putrefaction. He was unable to determine from his experi­
ence whether coagulable urine ever precedes the onset of
dropsy. He confirmed Wells’ observation that a bloody
sediment is found after an attack of scarlatina and sus­
pected that the use of calomel aggravated this state.
Perhaps Blackall’s single most important contribution,
when viewed with hindsight, was his demonstration that
mercurials were being abused and that the ‘mercurial hab­
it’ caused irritation and inflammation, and also dropsy.
He further ascribed some cases of fevers of children to the
excessive use of calomel.
In reviewing the 9 autopsies that he described in his
book, Blackall concluded that the urinary organs are often
free from any appearance of unsound structure, despite
the great fault in their secretion and that, in 2 mercurial
cases, the kidneys were firmer than normal.
Finally, Blackall posed the obvious question: where
does the coagulable part of the urine come from? He
refered to the earlier contention of Erasmus Darwin that
it enters the bladder by an inverted motion of the lym­
phatic system, but is quick to refute this by saying that it
has: ‘no kind of support from anatomy’. Could the dropsi­
cal accumulations supply the albumin in the urine, he
asks? As it is hardly ever found other than with dropsy,
and as the fluid is wholly unfit for the purposes of circula­
tion, he concluded that it is appropriate that it should be
discharged. He argued that the kidneys, from their ‘com­
parative simplicity of secretion’, are probably the ‘glands’
most suited for this purpose, as: ‘they appear to be pos­
sessed of a sort of selective power capable of separating
the blood from whatever is hurtful to it’. On the other
hand, he contended that this understanding does not
account for the presence of blood in the urine and noted
that, occasionally, coagulated urine had been observed in
patients without dropsy or in hydrocephalus where the
amount of accumulated fluid was small. Most important­
ly, the excretion of the coagulable substance increased
precisely when the disease was worst and decreased when
relief was obtained, contrary to his expectation that recov­
ery should be associated with an ‘unloading’ of the materi­
al into the urine.
Blackall was forced to conclude that he was uncertain
about whether the serum found in the urine was derived
from dropsical accumulations. At no point does disease of
the kidney as a cause of the coagulable urine rear its
The authors are appreciative of having been provided with an
unpublished English translation by Professor J.S. Cameron of Pierre
Rayer’s writings on the history of renal disease, which was invaluable
in the preparation of this paper.
4 Cruikshank WG: Experiments on urine and
sugar by Mr Cruikshank; in Rollo J (ed): Cases
of Diabetes Mellitus. London. J Dilly, 1798. pp
5 Wells WC: Observations on the dropsy which
succeeds scarlet fever. Trans Soc Improvement
Med Surg Knowledge 1812;3:167-186.
6 Blackall J: Observations on the Nature and
Cure of Dropsies and Particularly on the Pres­
ence of the Coagulable Part of the Blood in
Dropsical Urine. London, Longman, Hurst,
Rees. Orme and Brown. 1813.
7 Harris JD: The Royal Devon and Excter Hos­
pital. Exeter. Eland Bros, 1922.
8 Fourcroy AF. Vauquelin N: Mémoire pour ser­
vir à l'histoire naturelle clinique et médicale de
l’urine humaine. Mémoires de l’Institut 1797:
John Blackall and Dropsical Patients
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1 Southey R: The Lectures on Bright’s Disease.
Br Med J 1881;1:541-546, 587-589.625-627.
2 Rayer P: Traité des Maladies des Reins. 3 vol
with atlas. Paris, Ballière, 1839.
3 Cotugno D: De Ischiade Nervosa Commentarius. Vienna. R Graffer, 1790.
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