460 SECTIONAL TRANSACTIONS.—I. 
particular sort of engineer, one who specialises in the apparatus of respiration, such, 
for instance, as the diving engineer or the technical chemical defence departments of 
the National Armée. The amount of oxygen necessary is about a litre and a half 
per minute. If an ascent of 5,000 cubic feet were made in five hours the oxygen 
actually absorbed by the climber would be 450 litres. Suppose he breathed half that 
amount on the descent :— 
450 
225 
675: say 700 litres, say 30 cubic feet. 
The problem then may be subdivided thus :— 
1. How is a man to carry 30 cubic feet of oxygen ? 
2. If he ‘ rebreathes ’ it, how is he to get rid of the carbonic acid ? 
3. How is he to cope with the incidental difficulties proper to the use of apparatus 
such as the occurrence of water vapour, which freezes in inconvenient places ? 
4, An estimate of the margin necessary over and above the theoretical quantity. 
Seven hundred litres weigh approximately a kilogram, so that the weight of the 
oxygen itself is trifling, but the weight of an ordinary cylinder which would carry 
30 cubic feet of compressed gas is too great. What, therefore, are the lightest 
cylinders into which it could be compressed ? Were the problem one of providing 
a supply of air for a diver or a respirator for a soldier, a competent authority would 
sit down to face it on a basis of exhaustive experiment and extended drill. In the 
end I have little doubt that he would solve this problem and with less expenditure 
than is entailed in the equipment and expenses of successive expeditions to the 
Himalayas—expeditions which cost not only money but a toll of valuable lives. 
Mr. N. E. OpELL, member of the Everest Expedition, 1924. 
Dr. Raymonp GREENE, member of the Kamet Expedition, 1931. 
Monday, September 28. 
PRESIDENTIAL AppRESs by Dr. H. H. Dats, C.B.E., Sec.R.8., on The 
Biological Nature of Fultrable Viruses (see page 172). 
Discussion on The Biological Nature of Filtrable Viruses :— 
Dr. T. M. Rivers.—The Nature of Animal Viruses. 
For discussion Dr. Dale has chosen to characterise viruses by three negative 
properties, namely, invisibility by ordinary microscopic methods, failure to be retained 
by filters impervious to ordinary bacteria, and failure to propagate themselves in 
the absence of susceptible cells. I prefer a positive characterisation of the viruses, 
one emphasising the intimate relation between them and their host cells. Nevertheless, 
I have followed the cue given by Dr. Dale, who, incidentally, has posed many questions . 
that cannot be answered at the present time. 
Data concerning the filterability, visibility and cultivation of viruses are sufficiently 
adequate in quantity, but in many instances distinctly lacking in quality. Frequently, 
when observations are accurate, conclusions are unwarranted. According to reports, — 
many of which have come from eminent investigators, most of the viruses have been 
seen and have been cultivated on lifeless media. If these reports are correct it is 
obvious that such viruses are autonomous living agents, and that further discussion 
of their biological nature should deal with their place in the scale of life or with their 
relation to other forms of life. Evidently most workers do not consider the reliable 
data already acquired sufficient proof of the nature of the viruses. Therefore, if 
much of the information in the past has been incorrect or misleading, there is no 
reason to suppose that all of it garnered in the future will lack these faults. Conse- 
quently, investigators working in the virus field should demand experimental accuracy 
and intellectual integrity. 
A point in question is the increasing demand, made by certain workers, that 
viruses are merely filterable stages in the life-cycle of ordinary bacteria. It is 
