
- Fuly 27, 1871] 

NATURE 

253 

Stream is only a modified and partial cause of this general circula- 
tion. Now in the first place, as I have already said, it seems to me 
that the distribution of warm water in the North Atlantic has 
been traced to its source, and all the general phenomena of the 
Gulf Stream, its origin, its course, its extension, and its depth at 
certain points, have been froved by the careful {observations of 
many years, which I see no reason whatever to doubt. The 
constant impulse of the trade wind drives a broad current of 
equatorial water against the American coast. A great part of 
this current is observed to turn northwards through the Strait and 
round the islands, and to pour an eternal flood of hot water in a 
certain direction, under known laws, into the closed basin of the 
North Atlantic, and as a natural consequence the temperature is 
very considerably raised. 
We are undoubtedly most deeply indebted to Dr. Car- 
penter for the forcible way in which he has brought for- 
ward the arguments on the other side; and, after carefully | 
considering everything, I am thoroughly willing, with Sir 
John Herschel, to cede that ‘‘there is no refusing to admit 
that an oceanic circulation of some sort must arise from mere 
heat, cold, and evaporation as vere causa ;” and that ‘‘hence- 
forward the question of ocean currents will have to be studied 
under a twofold point of view ;” but my strong conviction is that 
if the sagacious philosopher whose loss we now deplore, had 
been spared so to study it, he would have only been strengthened 
in his verdict of 1861 as to the Gulf Stream, that there can be no 
‘possible ground for doubting that it owes its origin entirely to 
the trade-winds.” Dr. Carpenter attributes the general oceanic 
circulation, of which he regards the Gulf Stream as only a modi- 
fied case, to tropical heat and evaporation, and arctic cold, 
possibly aided by differences of barometric pressures ; or to con- 
yection pnre and simple, as illustrated in his experiments before 
the Royal Institution and the Geographical Society. Now 
what we expect of Dr. Carpenter before we are called upon 
to accept to the full his magnificent generalisation, is a calcula- 
tion and demonstration of the amount of the effect of the causes 
upon which he depends acting under the special circumstances. 
We must remember that heat is received by the ocean at the sur- 
face only, and that owing to cold indraughts all over the globe, so 
far as we know the temperature falls the deeper we go; that all 
our observations tend to show that the temperature of the sea is 
only influenced by direct solar radiation to any amount to the 
depth of fifty fathoms, so that all currents depending upon dif- 
ference between equatorial and polar temperatures must be pro- 
duced and propagated in a film of water about the depth of the 
height of St. Paul’s and 6,000 miles long. The black line 
bounding that chart represents pretty nearly the depth of the 
ocean, and even where the whole of the water supposed to be 
involved in the movement, it would be difficult to imagine a per- 
ceptible current to be produced in so thin and wide a sheet by 
such feeble cause. It would be impossible to indicate by the 
finest hair line the tenuity of the film which is actually affected 
by the direct rays of the sun. How differences in barometric 
pressure can produce constant currents I do not see. Rapid 
fluctuations in pressure in places within a short distance of one 
another will doubtless produce readjustment by a wave motion ; 
but constant differences of pressure will simply produce constant 
differences of level and no currents. Varying pressures at very 
distant points cannot possibly produce a constant current. I 
freely admit that I am quite incapable of undertaking the investi- 
gations which might lead to the estimation of the relative or 
actual importance of these causes of currents. I have several 
times put the question to specialists in such physical inquiries, 
but they have always said that it was a matter of the greatest 
difficulty, but that their impression was that the effects would be 
infinitesimal. 
I fear then that, in opposition to the views of my distinguished 
colleague, I must repeat that I have seen as yet no reason to 
modify the opinion which I have consistently held, that the re- 
markable conditions of climate on the coasts of Northern Europe 
are due in a broad sense solely to the Gulf Stream; that 
is to say, that while it would be madness to deny that in a great 
body of water at different temperatures, under varying barometric 
pressures, and subject to the surface drift of variable winds, 
currents of all kinds variable and more or less permanent must 
be set up, yet the influence of the great current which we call 
the Gulf Stream, the reflux in fact of the great equatorial cur- 
rent, is so paramount as to reduce all other causes to utter 
insignificance, 
WYVILLE THoMsON 


PHYSIOLOGY 
The Mouse’s Ear as an Organ of Sensation* 
Dr. Scuost, of Prague, who lately published a remarkable 
paper on the wing of the bat, has made similar researches 
on the ear of the white mouse, with very interesting and sur- 
prising results (in ‘‘Schultze’s Archiv,” vol. vii. p. 260.) The 
first thing which struck Dr. Schobl was the immense and 
“fabulous” richness of the ear innerves. Even the bat’s wing 
is but poorly supplied in comparison. The outer ear was care- 
fully divided horizontally through the middle of the cartilage into 
two laminz, each of which was found to be equally supplied 
with nerves, and was then examined by removing the epidermis 
and the Malpighian layer of the skin. In each of these laminz 
were discovered three distinct strata of nerves, which are thus 
described : The first or lowest stratum lies immediately upon the 
cartilage ; it consists of the largest trunks which enter the ear, 
5 to7 in number, and their next branches, varying from ‘074 mm. 
to ‘028 mm. in diameter. The mode of division of these trunks 
is mainly dichotomous, but they are connected by several different 
kinds of anastomoses ; as, for instance, by decussation of two 
adjacent trunks, by transverse or oblique connecting branches, 
by plexuses, by loops, &c. ; while branches also perforate the 
cartilage, and bring the nerves of the two halves of the ear into 
connection. The general distribution agrees with that of the 
larger blood-vessels. The second stratum lies immediately over 
the first, and is connected with it by a multitude of small 
branches, and by a fine marginal plexus at the outer border of 
the ear, which may be regarded as common to both. The 
diameter of its nerves is from ‘0185 mm. to ‘0098 mm. ; it lies 
immediately under the capillary vascular network of the skin, 
and has a generally reticulated arrangement, forming plexuses of 
very various shapes. The third stratum of nerves, developed 
out of the very finest twigs of the second, lies at the level of the 
capillary network ; it is composed of branches ‘oog8 mm. to 
0037 mm. in thickness, which (like those of the other strata) con- 
tain medullated nerve-fibres. It forms an extremely delicate 
network, like the second layer, but its finest branches may ter- 
minate in two ways, Some of them, each containing two to 
four medullated fibres, run directly to the hair follicles, and form 
a nervous ring round the shaft of the hair, terminating below the 
follicle in a nervous knot. Others, again, consisting of not more 
than two medullated fibres, bend towards the surface where the 
fibres lose their double outline, and form, immediately under the 
Malpighian layer of the skin, a fine terminal network of pale 
fibres, which is the fourth and ultimate stratum of nervous struc- 
tures. The terminal ‘‘knots” or corpuscles, and the nervous 
rings, are inseparably connected with hairs and their sebaceous 
glands, so that through the whole of the external ear no hair can 
be found without this nervous apparatus, and vice versd. The 
connection of the hair follicle with the nerve termination 
is as follows:—Under the bulk of the hair in each 
follicle is a more or less conical prolongation, com- 
posed of distinct nucleated cells, which run vertically down- 
wards, and is enclosed within the limiting membrane of the 
follicle. The nervoustwig which, as has been said, runs to each 
hair follicle from the third stratum of nerves, makes several turns 
round the shaft of the hair, and from the ring thus formed two to 
four nerve-fibres run vertically downwards to the prolongation 
of the follicle, immediately beneath which they form a knot. 
These knots are almost always spherical, sometimes oval, and 
about ‘015 mm. in diameter. Jn each square millimetre of the 
marginal part of the ear there are about 90 such bodies, and near 
the base perhaps 20, so that the average number may be 30. 
Calculating from the average size of the ear of a common mouse, 
it is then found that there are on the average 3,000 nerve termi- 
nations on each of its surfaces, making 6,000 on each ear, or 
12,000 altogether. The function of this elaborate arrangement 
would seem to be, like that in the wing of the bat, to supply by 
means of a very refined sense of touch, the want of vision to 
these subterranean animals. 


SCIENTIFIC SERIALS 
Part ii. of the Zetschrift fiir Ethnologie contains No. 6 ot 
Dr. Hartmann’s “ Studies of the History of Domestic Animals,” 
on the yak or grunting ox (Bos grunniens) living wild at immense 
altitudes in the mountains of Central Asia north of the Himalaya, 
and largely used in a domesticated state in Mongolia and 
* From the “ Quarterly Journal of Microscopical Science” for July. 
