
Marci 10, 1923] 
NATURE 
325 

the thousand publications of those who bark at the 
dead lion. 
As Prof. Dakin has been good enough to suggest 
that I am ignorant, may I supply him with proof and 
the readers of NaTurE with a test? I donot know 
what naturalists (the biologists of Prof. Dakin) mean 
their key-words “innate,” “ acquired,’ and 
““ inherited ’’ when applied to characters. Does Prof. 
Dakin know ? Will he tell us ? 
G. ARCHDALL REID. 
Southsea, February 19. 

A Relativity-predicted Mechanical Effect in the 
Electromagnetic Field. 
THE present writer would certainly starve if his 
bread depended on supplying a certain experimental 
verification here asked for. It should, however, be 
mere Boys’ play to those who measure the gravita- 
tional constant with a little pile of sovereigns and 
a quartz fibre, or who photograph the wake of a 
flying bullet. The mathematical argument leading 
to the prediction indicated below is sent to England 
by the mail carrying this letter, for publication, but 
I cannot say where and when it will appear. 
A body, say a crystal, at rest in an electromagnetic 
field should experience a force per unit volume, in 
Maxwell’s notation and in E. units, equal in 
magnitude and direction to 
dy, 2 
ae (DB - EH/47c*), 
where K is conduction current and c the velocity of 
light in vacuo. It is possible that. the third term 
has been given before, but I have not seen it any- 
where. The verification here asked for is that of 
the existence of this term. VEH is in the direction 
of a light ray and VDB is normal to the correspond- 
ay front. In an isotropic transparent body, VDB 
=h*(VEH/47c*), where & is the index of refraction. 
Unfortunately, 4c? is about 10 x 1-131, but my 
son, Dr. A. L. M‘Aulay, tells me that the magnitude 
of VEH may readily be made equal to 10%, so that 
the effect may be detectable. 
The term indicates that when a wave-train traverses 
a point the matter at the point is always urged 
along the ray towards the nearest wave-crest or 
wave-trough, and normal to the front from the nearest 
crest or trough. Can any reader suggest a plausible 
physical reason why this should occur ? 
I may remark that Maxwell's expression for the 
force per unit volume is 
V(K +dD/dt)B - ESyD, 
and that probably most relativists would drop the 
dD/dt from this expression. Let the physicist tell 
us which, if any, of the three expressions is verified 
experimentally. ALEX. M‘AvuLay. 
niversity of Tasmania, November 28, 1922. 
VKB - ESyD + 

The Measurement of the Rates of Oxidation 
and Reduction of Hemoglobin. 
WE have recently been engaged on the determina- 
tion of the velocities of the chemical reactions of 
hemoglobin. These are of interest both to the 
physiologist because of the important part played by 
this pigment in respiration, and also to the physical 
chemist because this pigment is an almost unique 
example of a large complex protein molecule which 
combines with gases in a simple chemical manner. 
* Some of the results that we have obtained and the 
NO. 2784, VOL. 111] 

methods we have used may therefore be of interest 
to readers of NATURE. 
In order to measure the rate of reduction two 
solutions were prepared: (a) a 1-5 per cent. solution 
of whole blood in tap water, (b) a solution of sodium 
hyposulphite (Na,S,0O,) in tap water which was 
rendered neutral to brom-thymol-blue by the 
addition of sodium carbonate solution. These two 
solutions were by suitable means forced under a 
pressure of, roughly, 500 mm. of mercury into the 
mixing chamber of the measuring apparatus through 
conical jets of small bore, so that the two solutions 
underwent vortex motion at a high rate of speed. 
Preliminary tests of the measuring apparatus, using 
as fluids a sodium hydroxide solution containing 
phenol phthalein and a rather stronger solution of 
acid, showed that mixing and chemical combination 
were complete with one measuring apparatus in less 
than 0-0055 sec., and with another apparatus in less 
than o-0005 sec. The mixed blood solution and 
reducing agent passed from the mixing chamber of 
the apparatus in use down a glass tube with known 
velocity, being examined at different positions by 
means of the reversion spectroscope, by which we 
could ascertain the ratios of those amounts of hamo- 
globin still combined with oxygen and those in the 
reduced state. 
We thus obtained the concentration of oxyhemo- 
globin (O,Hb) at a series of instants, the intervals 
between which could be readily obtained from the rate 
of linear flow of the solution down the tube, and the 
positions of the points examined by the spectroscope. 
Experiments on the rate of reduction of oxy- 
hemoglobin (O,Hb) by the reducing agent (Na,S.O,) 
have shown that with increase of concentration 
of the latter the rate of reduction increases to a 
maximum, beyond which it cannot be raised by a 
further increase. This we take to mean that the 
process consists of two stages: 
(1) Reduction of oxyhzmoglobin, 7.e. 
O,Hb->0O, + Hb. : 
(2) Removal of O, (liberated from O,Hb) by com- 
bination with the reducing agent. 
As the concentration of the reducing agent is 
increased, the free oxygen formed from O,Hb by 
stage I is removed more quickly, until a concentra- 
tion is reached at which the “ free’’ oxygen is re- 
moved so quickly that the reaction O,Hb->O, +Hb 
is not appreciably opposed by the reverse reaction 
O, +Hb->O,Hb. Further increase in concentration 
of the reducing agent cannot therefore further 
accelerate the velocity of the reduction of the O,Hb, 
the latter being now solely determined by the 
velocity of the reaction O,Hb—O,+Hb. We have 
other evidence in support of this view, which we 
hope to present at length elsewhere. The time 
taken for complete reduction of O,Hb when the 
concentration of Na,S,O, was sufficient to secure the 
“maximum ”’ rate of reduction was about 0-5 sec. 
at 12° C. This rate of reduction is such as to be a 
factor of importance in considering the conditions 
which determine the rate of uptake of oxygen by 
organs within the body. We found further that the 
logarithm of the concentration of O,Hb when plotted 
against time gave a straight line relationship, as 
should indeed be the case if the reduction of O,Hb 
is a monomolecular process. 
The measurements of the velocity of oxidation 
of haemoglobin required the preparation of large 
quantities of reduced hemoglobin solution. This 
was obtained by spraying a solution of blood in tap 
water heated to 50° C. into a large vacuous container, 
thus causing the gases combined with the hemoglobin 
to be liberated. This reduced blood solution {was 
mixed with water containing dissolved oxygen by 
K 2 
