OcTOBER 2, 1902] 
INCA MOMG ER 
569 
tissues will not contract in pure solutions of non-electrolytes like 
sugar or albumin. But different contractile tissues differ in the 
nature of the ions which are their most favourable stimuli. An 
optimum salt solution is one in which stimulating ions, like those 
of sodium, are mixed with a certain small amount of those which 
like calcium restrain activity. Loeb considers that the ions act 
because they affect either the physical condition of the colloidal 
substances (proteid, &c.) in protoplasm or the rapidity of 
chemical processes. 
Ameceboid movement, ciliary movement, the contraction of 
muscle, cell division and karyokinesis all fall into the same 
category as being mainly dependent on the stimulating action 
of ions. 
Loeb has even gone so far as to consider that the process of 
fertilisation is mainly ionic action ; he denies that the nuclein of 
the male cell is essential, but asserts that all it does is to act as 
the stimulus in the due adjustment of the proportions of the 
surrounding ions, and supports this view by numerous experi- 
ments on ova in which without the presence of spermatozoa he 
has produced larvae by merely altering the saline constituents 
and so the osmotic pressure of the fluid that surrounds them. 
Whether such a sweeping and almost revolutionary notion will 
stand the test of further verification must be left to the future ; 
so also must the equally important idea that nervous impulses 
are to be mainly explained on an electrolytic basis. But whether 
or not all the details of such work will stand the test of time, 
the experiments I have briefly alluded to are sufficient to show 
the importance of physical chemistry to the physiologist, and 
they also form a useful commentary on what I was saying just 
now about vitalism. Such eminently vital phenomena as move- 
ment and fertilisation are to be explained in whole or in part as 
due to the physical action of inorganic substances. Are not 
such suggestions indications of the undesirability of postulating 
the existence of any special mystic vital force ? 
I have spoken up to this point of physical chemistry as a 
branch of inorganic chemistry ; there are already indications of 
its importance also in relation to organic chemistry. Many 
eminent chemists consider that the future advance of organic 
chemistry will be on the new physical lines. It is impossible to 
forecast where this will lead us ; suffice it to say that not only 
physiology, but also pathology, pharmacology and even thera- 
peutics will receive new accessions to knowledge the importance 
of which will be enormous. 
I have now briefly sketched what appear to me to be the two 
main features of the chemical physiology of to-day, and the two 
lines, organic and inorganic, along which I believe it will 
progress in the future. 
Let me now press upon you the importance in physiology, as 
in al] experimental sciences, of the necessity first of bold ex- 
perimentation, and secondly of bold theorising from experi- 
mental data. Without experiment all theorising is futile ; the 
discovery of gravitation would never have seen the light if 
laborious years of work had not convinced Newton that it could 
be deduced from his observations. The Darwinian theory was 
similarly based upon data and experiments which occupied the 
greater part of its author’s lifetime to collect and perform. 
Pasteur in France and Virchow in Germany supply other 
instances of the same devotion to work which was followed by 
the promulgation of wide-sweeping generalisations. 
And after all it is the general law which is the main object of 
research ; isolated facts may be interesting and are often of value, 
but it is not until facts are correlated and the discoverers ascer- 
tain their inter-relationships that anything of epoch-making 
importance is given to the world. 
It is, however, frequently the case that a thinker with keen 
insight can see the general law even before the facts upon which 
it rests are fully worked out. Often such bold theorisers are 
right, but even if they ultimately turn out to be wrong, or only 
partly right, they have given to their fellows some general idea 
on which to work ; if the general idea is incorrect, it is important 
to prove it to be so in order to discover what is right later on. 
No one has ever seen an atom or a molecule, yet who can doubt 
that the atomic theory is the sheet anchor of chemistry ? 
Mendeléeff formulated his periodic law before many of the 
elements were discovered; yet the accuracy of this great 
generalisation has been such that it has actually led to the 
discovery of some of the missing elements. 
I purpose to illustrate these general remarks by a brief allusion 
to two typical sets of researches carried out during recent years 
in the region of chemical physiology. I do not pretend that 
No. 1718, VOL. 66] 
either of them has the same overwhelming importance as the 
great discoveries I have alluded to, but I am inclined to think 
that one of them comes very near to that standard. The in- 
vestigations in question are those of Ehrlich and of Pawlow. 
The work of Ehrlich mainly illustrates the useful part played 
by bold theorising, the work of Pawlow that played by the 
introduction of new and bold methods of experiment. 
I will take Pawlow first. This energetic and original Russian 
physiologist has by his new methods succeeded in throwing an 
entirely new light on the processes of digestion. Ingeniously 
devised surgical operations have enabled him to obtain the 
various digestive juices in a state of absolute purity and in large 
quantity. Their composition and their actions on the various 
foodstuffs have thus been ascertained in a manner never before 
accomplished ; an apparently unfailing resourcefulness in devising 
and adapting experimental methods has enabled him and his 
fellow workers to discover the paths of the various nerve im- 
pulses by which secretion in the alimentary canal is regulated 
and controlled. The importance of the psychical element in 
the process of digestion has been experimentally verified. If I 
were asked to point out what I considered to be the most im- 
portant outcome of all this painstaking work, I should begin 
my answer by a number of negatives, and would say, no the 
discovery of the secretory nerves of the stomach or pancreas ; 
not the correct analysis of the gastric juice, nor the fact that 
the intestinal juice has most useful digestive functions ; all of 
these are discoveries of which anyone might have been rightly 
proud ; but after all they are more or less isolated facts. The 
main thing that Pawlow has shown is that digestion is not a 
succession of isolated acts, but each one is related to its pre- 
decessor and to that which follows it; the process of digestion 
is thus a continuous whole; for example, the acidity of the 
gastric juice provides for a delivery of pancreatic juice in proper 
quantity into the intestine; the intestinal juice acts upon the 
pancreatic, and so enables the latter to perform its powerful 
actions. I am afraid this example, as I have tersely stated it, 
presents the subject rather inadequately, but it will serve to 
show what I mean. Further, the composition of the various 
juices is admirably adjusted to the needs of the organism ; 
when there is much proteid to be digested, the proteolytic 
activity of the juices secreted is correspondingly high, and the 
same is true for the other constituents of the food. It is such 
general conclusions as these, the correlation of isolated facts 
leading to the formulation of the law that the digestive process 
is continuous in the sense I have indicated, and adapted to the 
needs of the work to be done, that constitute the great value of 
the work from the Russian laboratory. Work of this sort is 
sure to stimulate others to fill in the gaps and complete the 
picture, and already has borne fruit in this direction. It has, 
for instance, in Starling’s hands led to the discovery of a 
chemical stimulus to pancreatic secretion. This is formed in 
the intestine as the result of the action of the gastric acid, and 
taken by the blood-stream to the pancreas. Whether this 
secretin as it is called may be one of a group of similar chemical 
stimuli which operate in other parts of the body has still to be 
found out. 
The other series of researches to which I referred are those 
of Ehrlich and his colleagues and followers on the subject of 
immunity. This subject is one of such importance to every 
one of us that I am inclined to place the discovery on a level 
with those great discoveries of natural laws to which I alluded 
at the outset of this portion of my Address. I hesitate to do 
so yet because many of the details of the theory still await 
verification. But up to the present all is working in that direc- 
tion, and Ehrlich’s ideas illustrate the value of bold theorising in 
the hands of clear-sighted and far-seeing individuals. 
But when I say that the doctrine is bold, I do not mean to 
infer that the experimental facts are scanty ; they are just the 
reverse. But in the same way that a chemist has never seen an 
atom, and yet he believes atoms exist, so no one has yet ever 
seen a toxin or antitoxin in a state of purity, and yet we know 
they exist, and this knowledge promises to be of incalculable 
benefit to suffering humanity. 
It may not be uninteresting to state briefly, for the benefit of 
those to whom the subject is new, the main facts and an outline 
of the theory which is based upon them. 
We are all aware that one attack of many infective maladies 
protects us against another attack of the same disease. The 
person is said to be zune either partially or completely 
against that disease. Vaccination produces in a patient an 
