42 Original Articles. (Jan. 
believe that this gas is in reality absent in sea-water at great depths.* 
From observations conducted many years ago by an eminent French 
experimentalist, M. Biot, it would appear that the swimming bladder 
of fishes contains a larger quantity of nitrogen than oxygen when they 
happen to have been captured near the surface ; and a larger quantity 
of oxygen than nitrogen when brought up from a depth of a few hun- - 
dred fathoms. The researches of other observers would also tend to 
confirm the view that the quantity of oxygen held in solution by sea- 
water increases rather than diminishes with the depth; and on 
theoretical grounds, moreover, there is reason to believe that the 
presence of oxygen is inseparable from the pressure which prevails at 
great depths. 
In the case of creatures belonging to the higher order, as, for 
example, fish, the conditions that have been laid down are no doubt 
indispensable. They cannot support life beyond a comparatively 
moderate depth ; and, as a general rule, it may be taken for granted 
that no living organism, demanding a supply of free air for its sus- 
tenance, or whose structure is of such a kind as to be inordinately 
affected by an increase of the pressure to which it is subject in shal- 
lower water, could, by any possibility, survive a single instant after 
descending lower than a few hundred fathoms. But there is a large 
class of creatures, inhabiting the ocean at ordinary depths, whose 
structure is so universally permeable by fluids that, assuming other 
conditions to be favourable and the transitions from a low to a high 
degree of pressure to be sufficiently gradual, it is immaterial whether 
the medium around them be pressed upon by one or by one hundred 
atmospheres. In the case of these creatures, as in that of a human 
being living under ordinary atmospheric pressure, it is only essential 
that the force should operate uniformly both within and without the 
body. Hence, in so far as mere pressure is concerned, there is no 
reason why creatures of the class referred to (and star-fishes are 
amongst the number) should not be able to exist at all depths. 
With regard to the previous manifestation of vegetable life which 
is said to constitute a condition essential to the existence of animals, 
both terrestrial and marine, it is only desirable to point out that, were 
this really a law cf nature, it would at once negative the assumption 
that animal life can be maintained at extreme depths ; for, if vegetable 
products are indispensable for the nutrition of the animal, and no 
vegetable structures are capable of living in default of a certain 
amount of light, inasmuch as no light can possibly penetrate to the 
profounder abysses of the ocean, animal existence must of course be 
rendered impossible. 
But whilst recent explorations of the sea-bed have indubitably indi- 
cated that animals can live at those vast depths, they would also seem 
to show that vegetable life, in any form at least in which we have 
heretofore detected it, is not co-existent; for whensoever vegetable 
structures have been found amongst the organic or inorganic matter of 
* M. Pasteur, the French chemist, in his recent experiments on Ferments, 
has sought to show that some of the so-called Infusoria are able to exist without 
oxygen. 
