TRANSACTIONS OF SECTION I. 743 
in equal degree with the capacity of discharging the function which it represents. 
The difficulty lies in this—that the physiologist finds himself compelled to use 
chemical language in a sense which the chemist does not recognise. What we 
mean thereby is that the hypothetical living molecule consists of a permanent 
part, which is not concerned in the performance of function, and of a collateral 
part, which is used, @.c., disintegrated in every transition of the molecule from the 
inactive to the active state, to be immediately reconstituted when action ceases. 
This notion of restitution is the nutshell in which the difficulty lies. All that we 
know about it is that the access of oxygen is an essential condition for its accom- 
plishment—oxygen not as an oxidiser, but as a restorer of functional capacity. 
I now propose to pass from the general to the particular, é.e., to the considera- 
tion of the chemical process of life as it presents itself in particular organs— 
namely, first in muscle and in nerve centre, and, secondly, in such glands as have 
up to this time been investigated—two groups of structures representing what 
Bichat called respectively animal life and organic life. On the general principle 
that in all our investigations we should proceed from the known to the unknown, 
muscle must be taken first, for its metabolism is more within reach of investiga- 
tion and is better understood than that of any other organ. 
When oxygen enters the living substance of muscle it is not as an oxidiser, 
but as a preparer and builder-up of material ready for explosion. For the muscle 
molecule receives two things from the blood, oxygen and oxidisable material ; 
but these two do not combine as a mere result of juxtaposition or of encountering 
one another. As Ostwald says, ‘Der freie Sauerstoff ist ein sehr trager Stott,’ 
at the temperature of the body. It cannot be brought into action in the living 
organism by a stimulus so long as it is in its free state. It must first become 
what Pfiiiger calls ‘intramolecular,’ and thereby change its Trigheit for mobility. 
The immediate effect of the access of oxygen is that the living substance of which 
it becomes a part becomes more susceptible to mechanical and electrical dis- 
turbance—i.c., more excitable than it was before. It requires, so to speak, to be 
wound up so as to become capable of discharging its oxidising function when 
awakened by a stimulus. Dr. Fletcher’s experiments, to which I will return 
later, show that the more perfect this preliminary anabolic process is, the more 
complete will be the catalysis. 
You will, I think, agree with me that in different stages of the metabolic 
process which is associated with muscular function oxygen acts in different ways— 
at one time taking part in an integrating process, for which we might, perhaps, 
employ the word oxygenation; at another in a process of oxidation, the molecule 
in which this occurs retaining its existence notwithstanding the disintegration of 
its oxidisable part. 
We have now to pass on to the question how oxygen takes part in the 
functional activity of the central nervous system. The only part of that system 
which is within reach of experimental investigation is the spinal cord. We have 
to consider in how far the results of investigations in the cord and in muscle 
agree or differ. 
Let me say on the threshold that our knowledge is largely due to work 
recently done at Jena and Géttingen under the direction of (or in co-operation 
with) Professor Verworn. I must first ask your attention to the method. 
More than thirty years ago Cohnheim taught us the use of a preparation 
which we used to call ‘the salt frog, in which the blood was replaced by 
physiological salt solution. He discovered that notwithstanding the defect of 
hemoglobin, and consequently of oxygen, the chief functions of life could be 
carried on. With much more perfect methods Verworn has followed Cohnheim. 
The improvement consists in this—that the circulation is maintained by 
mechanical means, so that by varying the rate of flow and the percentage of 
oxygen in the liquid the supply of oxygen to the cord can be increased or 
diminished at will. The effect produced is judged of by the mechanical 
responses to reflex excitation, the indications given by which are rendered more 
delicate by the previous administration of a trace of strychnine. The first step 
in the experiment is to establish a normal state of things by the circulation of 
