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which is formed of two metal capsules screwed together by the screw C, and
holding between them the membrane H. The two halves thus form a box.
When the two halves are ap-
proximated, the box is closed .ji ..v
except at one point K, opposite i£_ :
the hinge, where there is an

opening to allow the passage of 1 '-, | '

the renal vessels and nerves, I | x

and the ureter to the kidney, I i y

which is placed within the box. I i -^j-p

During use, the space between
the membrane and the metal
box is filled with warm oil
through the opening in the '■ - -
screw. The opening in one-half
is then closed with a plug, '''i ■ ; ^ " " '';

while the other communicates i "' J. '

by a tube E, with the onco- u „. ^ . |_ 1_ '

graph. It is evident that any 4iiyi;7:'rL>irii.i - __,

change in the volume of the r

kidney will be communicated Vj : ;

to the oil between the mem- '■

brane and the capsule, oil being ^ig. 61.— Roy's oncograph. Diagrammatic section,
driven out into the tube t. The cylinder M is filled with oil, and com-

when the kidney swells, and municates by the tube K with the oncometer.

■1 ■ 1 1 • T 4.1 Changes in the height of the oil are communi-

being sucked m dn^ectly any ^^^^^j- ^^^ p.^^^ - ^ ^^ ^^^ j^^^^, ^ ,1^^ 3^.

shnnkmg of tlie kidney occurs, ciu-sions of which serve therefore as an index of

The oncograph, which is prac- the changes in volume of the kidney,

tically a piston - recorder, in

which the piston is made oil-tight by resting on a loose peritoneal membrane
tied round the tube, serves to register the amount of oil driven out or sucked
into the oncometer, and therefore at the same time the changes in the volume
of the kidney.

A simpler and more efficacious form of oncometer, in which air instead of oil
is used, has been devised by Schaf er ^ for the spleen, but is equally applicable
to the kidney. A description of it will be found in the section dealing with
the physiology of the circulation.

Nerve siqyply. — Before discussing the effects of various operative
procedures on the circulation of the kidney, it will be necessary to say a
few words concerning the nerve supply to this organ, since its vessels,
like those of all other parts of the body, are under the direct control of
the central nervous system.

The gross distribution of nerves to the dog's kidney has been the
subject of a careful investigation by Nollner ^ in Eckhard's laboratory.

1 Journ. Physiol., Cambridge and London, vol. iii. p. 205. ^ lUcl., 1896, vol. xx.

■' Beitr. z. Anat. u. Physiol. {Eckhard), Giessen, 1869, Bd. iv. S. 139.



644 THE SECRETION OF URINE.

The course taken by the nerves is very variable. The nerves are derived
from the sympathetic chain. From the gangha lying on the head of the
thirteenth rib, or from the cord immediately below this, is given off' a
large nerve (larger than the continuation of the sympathetic chain),
which perforates the crus of the diaphragm, and is called the large
splanchnic nerve. Between this ganglion and the next two or three
gangha below, are given off three or four smaller filaments, known as the
small splanchnic nerves. (It must be noted that this termmology is not
comparable with that employed in human anatomy, where the term
splanchnics is confined to the nerves given oft' by the sympathetic chain
while in the thoracic cavity.) These large and small splanchnics form a
plexus situated behind the suprarenals, and from which filaments are
given off to the coeliac and superior mesenteric ganglia and solar plexus.
From the plexus behind the suprarenals arise a number of filaments,
which form a meshwork in the fat and connective tissues between the
suprarenal and kidney, and then pass to the kidney around, and closely
applied to, the renal artery.

According to v. Wittich,^ the renal nerves in the rabbit, dog, and man
consist of two parts ; one part of them forms a plexus closely investing
the renal artery, while the other consists of several filaments which enter
the kidney parallel to the vessels, and can be traced along these as far
as the cortex.

The termination of these nerves in the kidney has been recently inves-
tigated by Berkeley,- using Golgi's method. He finds that from the vascular
nerves fine filaments arise to be distributed throughout the cortical and
medullary regions in the form of a vast open network. The glomeruli are
surrounded by a wide-meshed plexus of fibres, having terminal end knobs,
approximated closely to Bowman's capsule, but not penetrating that membrane,
nor passing to the glomerular capillaries. Fibres also pass off from the vascular
plexus to be distributed upon the convoluted tubes, with terminations which
penetrate the membrana propria of the tube, presumably to enter the cement
substance between the epithelial cells. Berkeley looks upon these latter nerves
as probably secretory in function.

With regard to the connection of the renal nerves with the central
nervous system, Bradford ^ has shown that, so far as the efferent nerves
to the renal vessels are concerned, these leave the spinal cord through
the anterior roots. Most of the fibres are contained in the eleventh,
twelfth, and thirteenth dorsal nerve roots.

Influence, of hlood fiow on secretion of urine. — We are now in a
position to consider the influence exerted by changes in the circulation
through the kidney on the secretion of urine. It must be remembered
that a rise of general blood pressure does not necessarily carry with it an
increased pressure in the glomerular capillaries or an increased blood flow
through the kidney. Thus, under many conditions, a rise of general
blood pressure is brought about by a constriction of all the visceral
arteries, including those of the kidney, and such constriction is more
than sufficient to counteract the effects of the increased blood pressure.
If we take a tracing of the kidney volume, for instance, in asphyxia, we

^ Konigsberger, Med. Jahrh., Wien, 1860, Bd. iii. S. 52 (quoted from Heidenhain in
Hermann's ' ' Handbuch ").

" Journ. Path, and BaetcrioL, Edin. and London, 1893, vol. i. p. 406.
'^ Journ. ThysioL, Cambridge and London, 1889, vol. x. p. 358.



INFLUENCE OF BLOOD PRESSURE. 645

find, coincident with the rise of general Ijlood pressure, a marked
shrinking of the kidney. On the other hand, a dilatation of the renal
vessels may be ineffectual to produce aii increased flow through this organ,
if at the same time there is a large fall of general blood pressure due
to dilatation in other parts of the body. We may consider, in the first
place, experiments in which the chief change has been in general blood
pressure. It is found that, if the aortic pressure sinks below 40 mm. Hg,
the urinary secretion stops absolutely. So long as the aortic pressure is
above this height, the secretion is more or less proportional to the
pressure, and changes with the changes in this pressure. Thus, if we
stimulate the vagus in the neck, using currents sufficiently strong to
produce a slowing of the heart-beat and a fall of blood pressure, there is
a shrinking of the kidney and a diminution in the urinary flow (GoU).
That this diminution in the flow is directly conditioned by the change in
blood pressure due to the cardiac inhibition, is shown by the fact that
stimulation of the vagi below the diaphragm is without effect on the
urine (Eckhard).

We may also alter the aortic pressure Ijy bleeding the animal to a
considerable amount, and later on reinjecting the blood so withdrawn.
It is found that after the bleeding, while the blood pressure is diminished,
the flow of urine is also lessened, but the flow increases when the blood
pressure is raised by reinjecting the blood which had been withdrawn.

If the aortic pressure be raised by ligaturing a number of the larger
arteries, the increased flow of blood through and the increased pressure in
the kidneys are attended with increased secretion of urine. Thus in one
experiment in which GoU ^ ligatured both carotids, both femorals, and
both ascending cervical arteries, the urine was increased from 8 "7 grms
in 30 minutes before the ligature, to 21-2 grms. after the ligature, while
the pressure in the aorta was raised from 127 to 142 mm. Hg.

Division of the spinal cord. — If the spinal cord be divided in the
upper cervical region, the result is a great fall in general blood pressure,
which may be as low as 30 to 40 mm. Hg. In all cases where the blood
pressure falls below 40 mm. Hg, the flow of urine is absolutely abohshed.
Since the renal vessels, like those of all other parts of the body, are kept
in a condition of tone by impulses descending from the vasomotor centre
in the medulla, division of the path of these impulses must cause a
relaxation of the renal vessels, which by itself would tend to occasion
increased blood pressure in the glomeruli. As a result of the section,
however, the vessels all over the body are relaxed, so that the capacity of
the vascular system is increased and the peripheral resistance diminished,
both factors concurring to produce the large fall of pressure observed.
This fall of pressure is more than sufficient to counterbalance the local
renal dilatation, so that there is diminished blood flow through the
kidney, as is shown by the marked shrinking of the oncometric curve of
the kidney on section of the cord.

Stimulation of the eorcU — If the peripheral end of the divided cord be
stimulated with an induction current, universal constriction of the blood
vessels and a large rise of blood pressure are produced. This, however, is
incompetent to bring back the urinary flow which has been abohshed by
the previous section, since the renal vessels concur in the general con-
striction, and the kidney shrinks still further in spite of the raised blood
pressure. If, how^ever, this local constriction be prevented by previous

1 Ztschr.f. rat. Med., 1854, N. F., Bd. iv. S. 86 (quoted by Heidenliaiu).



646 THE SECRETION OF URINE.

di^dsion of all the renal nerves, stimulation of the cord causes a large
expansion of the kidney and brings back the urinary flow.

Influence of the splanclinics} — The effects of stimulating the splanch-
nic nerves are very similar to those obtained from the stimulation of the
cord. As in the latter case, a large rise of general blood pressure is
produced, but the constriction of the renal vessels more than counteracts
the effects of this rise, so that the kidney shrinks and the flow of urine
is diminished or abohshed. The effects of dividing the splanchnics vary
in different animals. In the rabbit, where, in consequence of the extent
of the vascular area supphed by this nerve, a considerable fall of general
blood pressure is produced, no increase in the urinary secretion is
observed. In the dog, on the other hand, the lasting effect on the aortic
pressure is msignificant, so that the relaxation of the kidney vessels
caused by the section induces a largely mcreased flow through this organ,
and a marked increase in the flow of urine.

Influence of renal nerves. — Division of the renal nerves on one side
causes vasomotor paralysis in the organ of that side. The kidney there-
fore swells, and the flow of urine is increased. The swelling and
secretion is still further increased if the general blood pressure be raised
by stimulation of the splanchnics or spinal cord. Stimulation of the
renal nerves causes constriction of the vessels and diminished flow of
urine.

Bradford 2 has brought forward evidence to show that vaso-dilator
fibres run to the kidney with the constrictors, in the eleventh, twelfth, and
thu'teenth dorsal nerve roots. If the anterior roots of these nerves be
stimulated with induction shocks, repeated at the rate of one per second,
the effect is often a marked swelling of the kidney without any rise of
blood pressm-e sufficient to account for the enlargement. A similar
active dilatation of the vessels may be brought about reflexly by stimulat-
ing the posterior roots of these nerves. We have no du-ect experimental
evidence as to the influence of this active vascular dilatation on the
renal secretion, although it is extremely probable that a similar condi-
tion is the chief factor in the production of the extreme hydruria met
with in hysteria and other nervous affections.

Constriction of renal artery. — In some of the earliest researches on the
connection between the blood flow through the kidney and the uriuary
secretion, it was sought to affect the circulation by direct mechanical
constriction of the renal artery. Hermann,^ who carried out experi-
ments of this nature under Ludwig's guidance, showed that when the
artery was constricted to a considerable extent, the result was a dimin-
ished flow of lU'ine. If the constriction were carried so far that the
circulation of the kidney was entirely stopped, the flow of uriue instantly
ceased. So far these results are those one would expect on the filtration
hypothesis. It is found, however, that the flow of urine is not restored
at once on relieving the constriction, and that after a few minutes' total
cessation of the renal circulation, more than an hour may elapse between
the restoration of the circulation and the recommencement of the secre-
tion. We have seen that in the case of lymph formation, where a
process of filtration almost certainly comes into play, a temporary
iscluemia increases the permeability of the vessel wall, so that, on the

^ See especially Eckliard, .Beitr. r:, Anat. u. Physiol. {Eckhard), Giessen, 1869, Bd. iv.
S. 132, and 153-193.

- Loc. cit. " Loc. cit.



A CTION OF DIURE TICS. 647

subsequent restoration of the blood flow, the amount of lymph transuded
is greater than before the ligature. In the kidney the reverse is the
case. A temporary ischa^mia abolishes the flow for a considerable period
after the obstruction has been relieved. This fact shows that, for the
normal production of urine, the integrity of the living cells between the
blood and Bowman's capsule is necessary ; but I do not think that it
can be looked upon as definitely proving the active co-operation of these
cells in the process. In the kidney we have two layers of cells, the
vascular endothelium and the glomerular epithelium, intervening between
the blood and urinary tubule, and we have no evidence to guide us as to
the effects of temporary ischeemia on the glomerular epithelium. We
know that in a certain sense it becomes more permeable, inasmuch as
the urine which is first secreted after the restoration of the circulation
contains albumin, which may be traced on its way through the glome-
rular epithelium into the capsule. But this fact in itself might tend to
impede the flow of water through the glomerular membranes.

LigatuTG of renal vein. — In the case of lymph formation, a rise of
venous pressure tends to increase the amount of lymph produced. In
the kidney, ligature of the renal vein stops the flow of urine at once,
although it must send up the pressure in the glomerular capillaries to a
height approaching that of the renal artery. Now, in this case there are
three factors which might be concerned in causing the cessation of
secretion : the blood flow through the kidney is checked ; the cells of
the glomerular epithelium are asphyxiated ; and the engorgement of the
renal veins causes the interlobular veins to swell up and press on the
adjoining collecting tubules. Heidenhain lays most stress on the first
factor, and, relying mainly on this experimental result, concludes that
the chief agent in exciting glomerular activity is not the blood pressure
in the glomerular capillaries, but the rapidity of the flow through the
capillaries. On the other hand, Ludwig has shown that the effect of the
swelling of the interlobular veins is to obstruct the urinary tubules ; and
he looks upon the cessation of flow as entirely due to this mechanical
obstruction. It is impossible at present to decide which of these
explanations is correct, or indeed whether all of them may not be
involved.

Action of diuretics. — Since the main office of the kidney is to assist
in maintaining the normal constitution of the blood by freeing it from the
waste products of tissue metabohsm, we should expect it to react and to
be sensitive to slight changes in the composition of the blood. As a
matter of fact, we find that such is the case, and that the easiest way to
excite the urinary flow is by altering the composition of the blood,
through the administration of large quantities of water, or of certain
drugs which are known as diuretics. Of these bodies the only ones we
need discuss are the large class known as saline diuretics and the drugs
caffein and digitalis.

Saline diuretics include practically all crystalloid substances, which
can be injected into the blood in considerable quantities. As examples,
we may cite urea, dextrose, sodium chloride, potassivim nitrate, sodium
acetate, etc. If these bodies be injected into the blood, a very copious
secretion of urine is soon evoked, even if, previously to the injection,
the secretion had been at a standstill. In experiments on the excised
kidney, it has in most cases been found necessary to add urea or some
other substance of this group to the defibrinated blood used for the



648 THE SECRETION OF URINE.

artificial circulation, before any secretion could be obtained.^ On
inquiring into the mode of action of these bodies, we find that their
injection is followed by a slight rise of blood pressure accompanied with
a marked expansion of the kidney, and this expansion lasts throughout
the period of increased urinary flow. These effects are observed even
after all the renal nerves have been severed, so far as is practically
possible, and it has therefore been concluded that the changes in volume
of the kidney must be due to the substances acting either upon some
peripheral vasomotor mechanism, or even more directly upon the blood
vessels themselves. Since the increased secretion of urme is cotermin-
ous with the increased blood flow through the kidney, it is natural to
place these two events in the relation of effect and cause. To this con-
clusion it has been objected that one may frequently observe an absolute
standstill of secretion, with a high aortic blood pressure changed into a
copious secretion by the injection of one of these bodies, although the
blood pressure has been practically unaltered. Heidenhain and others
with him, therefore, look upon the action of these bodies as secretomotor.
Against the specific secretomotor action, either of urea or of the salines,
the following arguments may be brought forward. V. Limbeck ^ has
shown that the power of these bodies to induce urinary secretion on
injection into the blood stream is proportional to their power of attracting
water ( Wasseranziehungsvermogen), and is thus a function of their mole-
cular weights. Now it has been proved ^ that the result of injecting these
bodies into the blood is to cause an active flow of water from the tissues
into the blood, which therefore becomes diluted to an extent varying with
the osmotic pressure of the substances injected. The final effect, there-
fore, is the same as if a solution of the substance isotonic with or normal
to the blood had been injected into the circulation, and a condition
of hydremic plethora thus induced. We know that a condition of
hydremic plethora is associated with dilatation (especially of the visceral
vessels), general rise of capillary and venous pressures, and increased
rapidity of blood flow. The fact that the diuretic action of these bodies
is proportional to their osmotic pressures, implies that it is also propor-
tional to the hydrsemic plethora produced by the injection ; and it seems
probable, therefore, that the plethora is the chief agent in causing, first,
the vascular changes in the kidney, and secondly, the diuresis. If these
bodies acted as specific stimulants of the kidney, we should expect the
increased flow of urine to continue until all the substance injected had
been excreted. Such, however, is not the case. The diuresis comes to
an end when only a small amount of the injected substance has been
excreted, and lasts little or no longer than the hydremic plethora which
accompanies it.

Of the other diuretics, the action of two, caffein and digitalis, has been
very fully investigated. If half a grain of caffein be injected into a vein,
the kidney after a few seconds diminishes in volume, and the flow of urine
is lessened or entirely arrested. This contraction soon passes off', and is
followed by a rapid expansion, which is more considerable and lasts much
longer than the preceding contraction. Simultaneously with the beginning

1 M. Abeles, Sitzungsh. d. k. Akad. d. JVissensch. , Wieii, 1883, Bd. Ixxxvii. ; I. Muiik,
Virchoiv's Archiv, 1886, Bd. cvii. S. 291 ; ibid., S. 187 ; and I. Munk and Senator,
ibid., 1888, Bd. cxiv. S. 1.

^ Arch. f. cxpcr. Path. u. PharmakoL, Lei\r/Ag;, 1889, Bd. xxv. S. 69.

^ V. Brasol, Arch. f. PhynoL, Leipzig, 1884, S. 211 ; Starling, Journ. Physiol., Cam-
bridge and London, 1894, vol. xvii. p. 30 ; Leathes, ibid., 1895, vol. xix. p. 1.



LIGATURE OF THE URETER. 649

of the expansion, the urinaiy flow recommences and becomes much more
rapid than it was previously to the injection of the drug. On the general
blood pressure the injection of caffein causes an initial slight fall, followed
by a return to normal or a little above normal. In this case we seem to
be dealing with a drug, the most important action of which is on the
renal vessels, and it is probable that the increased pressure in and flow
through the glomerular capillaries induced by the drug is largely
responsible for the augmented flow of urine. According to von
Schroder,^ it is possible, by the administration of chloral, to abolish the
vaso-dilator effect of caffein in rabbits without destroying the diuretic
action of the drug ; but too mucli reliance cannot be placed on this
statement, since the volume of the kidney was not measured in this
observer's experiments.

The eff'ect of digitalis is rather more complex. It slows and
strengthens the cardiac beat, and at the same time constricts the smaller
arteries of the body, so that the arterial pressure is raised. In heart
disease the result of the improved working of the cardiac pump is to
relieve the venous pressure, increase the arterial pressure, and so bring
about an improved blood flow through the kidney. In such cases, there-
fore, digitalis acts as a powerful diuretic. In the healthy animal the
effect of this drug is more doubtful. It causes a constriction of the
renal vessels and therefore a shrinking of the kidney. Under certain
circumstances, however, it does exert an appreciable influence in causing
diuresis, which we may either explain, with Bradford and Phillips,^
as due to a direct action of the drug on the renal epithelium, or to the
fact that the rise of blood pressure more than counteracts the renal
constriction, so that there is an increased blood flow and pressure in the
glomerular capillaries.

Effects of ligature of the ureter. — If we are to look upon urine as a
filtrate, the amount of it must vary as P — p, where P represents the
pressure in the glomerular capillaries, while p represents the pressure at
the beginning of the urinary tubule. So far, we have only considered
the eff'ects of altering P, and have seen that, in the majority of cases at
any rate, the secretion of urine rises and falls with this pressure. Under
normal circumstances p is so small that it may be neglected, but we
ought to be able to diminish the flow of urine by increasing p. If the
ureter be obstructed by connecting it with a mercurial manometer, it
will be found that the mercury in the manometer rises quickly to 10 or
20 mm. Hg, and then more slowly until, in the dog, it may attain the
height of 50 or 60 mm. Hg, at which pressure the mercury column
remains stationary. The pelvis of the kidney and the ureter above the
ligature are now strongly distended ; the kidney is swollen, and a marked
oedema is soon observed extending to the perinephritic tissues, while
the lymphatics of the hilus are distended with clear fluid. Some hours
later, haemorrhages are found in the fatty cajDsule and in the pelvis and
ureter. Ludwig interpreted these results as determining the conclusions
he had already drawn from the eff'ects of section of the spinal cord, i.e.,
that, for the production of urine, a certain mmimum difference of
pressure P — p is necessary, and that the difference might be reduced
below this limit either by diminution of P or by augmentation of p.



Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 91 of 147)