As additional features of the subclass may be mentioned the absence of a corpus callosum connecting the right and left hemispheres of the brain,' and of a fossa in the septum between the two auricles of the heart.
In the New World, as already explained, the path of communication between the northerri and southern hemispheres has always been more or less open, and the temperate flora of southern America does not exhibit the isolation characteristic of the southern region of the Old World.
The forebrain forms the bulk of the whole brain, but the large size of the hemispheres is due to the greater development of the basal and lateral portions (pedunculi cerebri and corpora striata), while the pallium (the portion external to the lateral ventricles) is thin, and restricted to the median side of each hemisphere.
There is very little grey matter in the cortex of the hemispheres, the surface of which is devoid of convolutions, mostly quite smooth; in others, for instance pigeons, fowls and birds of prey, a very slight furrow might be compared with the Sylvian fissure.
The right and left lobes themselves are rent asunder (so to speak), so that they are freely visible from above, filling the corners formed by the hemispheres and the cerebellum.
Several futile attempts have been made to draw conclusions as to the intelligence of various birds, from comparison of the weight of the whole brain with that of the body, or the weight of the hemispheres with that of other parts of the central nervous system.
Bitumen is, in its various forms, one of the most widel y -distributed of substances, occurring in strata of every geological age, from the lowest Archean rocks to those now in process of deposition, and in greater or less quantity throughout both hemispheres, from Spitzbergen to New Zealand, and from California to Japan.
The shell thus formed is then cut along the line of the intended equator into two hemispheres, they are then again glued together and made to revolve round an axis the ends of which passed through the poles and entered a metal meridian circle.
Throughout the northern regions of both hemispheres there are several breeds of semi-domesticated dogs which are wolf-like, with erect ears and long woolly hair.
6 a Oligocene of both hemispheres appears Protapirus, which ranges well into the Miocene, and is essentially a tapir, having lost the third lobe of the last lower molar, and being in process of acquiring molar-like upper premolars, although none of these teeth have two complete inner columns.
Members of the group have existed in both east and west hemispheres since the beginning of the Miocene period; but in America they all became extinct before the end of the Pliocene period, and in the Old World their distribution has become greatly restricted.
Cavendish proved it by enclosing a metal sphere in two hemispheres of thin metal held on insulating supports.
If the sphere is charged and then the jacketing hemispheres fitted on it and removed, the sphere is found to be perfectly discharged.
Izerbacea and arctic species generally, to 1 oo ft., and occurring most abundantly in cold or temperate climates in both hemispheres, and generally in moist situations; a few species occur in the tropical and sub-tropical portions of the three great continents.
The cerebral hemispheres in existing Ungulates are well convoluted.
If the globe is divided into hemispheres by the meridians of 20° W.
A great circle can be drawn upon a terrestrial globe in such a way as to divide it into two hemispheres, one of which contains the greatest amount of land and the other the greatest amount of sea of any possible hemispheres.
What may be called typical, that is to say arboreal, squirrels are found throughout the greater part of the tropical and temperate regions of both hemispheres, although they are absent both from Madagascar and Australasia.
The polar or white bear (Ursus maritimus), common to the Arctic regions of both hemispheres, is distinguished from the other species by having the soles of the feet covered with close-set hairs, - in adaptation to the wants of the creature, the bear being thereby enabled to walk securely on slippery ice.
For the genus Elotherium, of the Lower Miocene and Upper Oligocene of both hemispheres, which is often placed next the Suidae, see ARTIODACTYLA.
And the smooth hemispheres of the brain do not extend backwards so as to cover any part of the cerebellum.
The genus which is common to the northern parts of both hemispheres is distinguished by the large cheek-pouches and by the absence or rudimentary condition of the claw of the first hind-toe, resembles Tamias in the slender form of the body, but displays great variation in the length of the tail, which may be a mere stump, or comparatively long.
The genus is common to the northern half of both hemispheres, and its members burrow and hibernate.
These efforts in the two hemispheres are based on the idea that international differences can be adjusted without war, where the parties are honestly aggrieved.
Taking two hollow hemispheres of copper, the edges of which fitted nicely together, he exhausted the air from between them by means of his pump, and it is recorded that thirty horses, fifteen back to back, were unable to pull them asunder until the air was readmitted.
On some of these occasions aurora was brilliant in both the northern and southern hemispheres, whilst magnetic disturbances were experienced the whole world over.
This condition is more than usually readily induced when the cerebral hemispheres have been removed.
Suspension of cerebral influence exists even more markedly, of course, when the cerebral hemispheres have been ablated.
Having regard to the special precautions taken to eliminate systematic error, and to the fact that the stars used were distributed nearly equally over both hemispheres, it is fair to conclude that this is the most accurate determination yet made.
These isothermal lines will be found to vary frommonth to month over the two hemispheres, or over local areas, during summer and winter, and their position is modified by continental or oceanic conditions.
Starting from the fact that if an electrified globe, placed within two hemispheres which fit over it without touching, is brought in contact with these hemispheres, it gives up the whole of its charge to them - in other words, that the charge on an electrified body is wholly on the surface - he was able to deduce by most ingenious reasoning the law that electric force varies inversely as the square of the distance.
The largest genus of the order, the sedges, is widely distributed in the temperate, alpine and arctic regions of both hemispheres, and is represented by 60 species in Britain.
Sporobolus, a large genus in the warmer parts of both hemispheres, but chiefly America, derives its name from the fact that the seed is ultimately expelled from the fruit.
With the primitive five-toed Amblypoda, as represented by the coryphodon, we again reach a northern group, common to the two hemispheres; but there is not improbably some connexion between this group and the much more specialized Barypoda, as represented by Arsinoitherium, of Africa.
Vallisneria (eel-grass) contains two species, one native of tropical Asia, the other inhabiting the warmer parts of both hemispheres and reaching as far north as south FIG.