As eight pair of nerves, according to Gall, are derived from the spinal marrow, they are styled "entering nerves;"but there are some minute nervous filaments, returning from the brain, which he calls "retrograde nerves. "These, he thinks, arise from the cortical substance which surrounds the ends of the first species of entering nerves. They unite in their course towards the spinal marrow, and increase in bulk, without passing through any ganglia. These nerves, in his opinion, form commissurae. Thus the commissure of the retrograde acoustic nerve is situated under and behind the pons varolii; that of the olfactory nerve between the ganglion belonging to these nerves; that of the retrograde nerves of the cerebellum in the pons varolii itself. The commissure of the retrograde nerves of the cerebellum are the corpus callosum, the commissura anterior of the lobe of the brain, near the optic nerves, continued in the septum lucidum, etc. Through the very middle of the spinal marrow, to a raphe or seam on the top of the corpus callosum, a very delicate medullary substance is observed to ascend, which Dr. Gall considers as the uniting medium of the double system of organs in the animal machine; an office we have assigned to the great intercostal.

It will be obvious on examining this system, that little difference can arise in any disquisition respecting the functions of the brain, whether it be derived from the spinal marrow or the contrary; and, ascending from the more simple structure, we may as well suppose a cerebral organ added, as, in descending, to view the lower animals deprived of it. The brain, we find, is not essential to animal life; for the nerves subservient to it are derived from another source; and it is certain, that a wound in the spinal marrow is more fatal than one in the brain. The functions of the latter, as we have seen, may be destroyed, while those of the former remain. So far, perhaps, the balance may be said to turn in favour of Dr. Gall. The brain, however, is the chief seat of the intellectual functions; and this is acknowledged by our author, since, in his "Organology" he has assigned to its different parts various passions and propensities. We have already admitted his chief position, that the shape of the cerebrum and cerebellum determine that of the skull; and, as he has found (or thinks he has found) certain projections connected in man and different animals, with different propensities or passions, he has denominated these their seat. He seems to have carried this enquiry to a considerable extent; and his collection of skulls, or casts, is said to be numerous and highly curious, as they belonged to characters the most notorious, of very different descriptions. On a careful examination and consideration of this system, we cannot think it wholly fanciful, though fancy seems often to predominate. But this is from our present subject. We shall return, however, to Dr. Gall's system, with some notice of that of Lavater, under the article Chaniology.

We must not conclude this descriptive part of the cerebrum, without some notice of the enquiries of Camper. This very accurate anatomist examined, with peculiar and discriminated attention, the skulls of different races of mankind; and found that the facial line, viz. the direction of a ruler applied to the lips and forehead, distinguished the more perfect and beautiful forms, from those confessedly less generally pleasing. The line of the faces of the ancient heads formed, with a horizontal line, an angle of 100°; beyond that is the deformity of the hydrocephalus; between it and 70° the usual European forms: a less angle than 70° marks the Calmuc, the negro, the ape, the dog, and the woodcock, in succession. In the last the angle is almost wholly lost. When we trace the forms of the different races of mankind in the natural history of man, we shall enlarge on this subject. It is only necessary at present to observe, that the direction of the facial line is marked by the projections of the hemispheres of the cerebrum, and the situation of the foramen occipitale. These distinguish the more perfect races; and, indeed, mankind, from its nearest resemblance, the ape.

The functions of the brain are so singular and important, that every art has been employed to trace its structure and component parts. When the knife of the anatomist had exhausted its dexterity, injections and microscopical observations came in aid. The cineri-tious matter, we have said, is vascular; but we added that the whole could not be injected. Some authors have thought that the whole has been filled; but this is not probable, nor supported by the experiments of the most accurate anatomists. Veins are traced from it, and their contents are conveyed to the sinuses. The parts not injected have been supposed, from microscopical observations, to be follicles; and small globular bodies have been discovered. But these are seen in almost every fluid of the human body, particularly in mucilaginous ones, and lead to no important consequence. The hemispheres of the cerebrum are chiefly mucilaginous; but as we approach the basis of the skull, a fibrous texture is more conspicuous: and, if the brain be macerated in acids, this fibrous structure can be traced further into its substance than by mere anatomical investigation. When the brain is boiled in oil, it assumes a granulated appearance.

The refinements of modern chemistry have also tortured this substance with as little profit. We recollect only the labours of M. Thouret, in the 38th volume of the Journal de Physique, p. 329, and M. Fourcroy's, in the 16th of the Annates de Chimie. The brain they found somewhat heavier than water; and consequently, a person at rest in a horizontal position in water, swims indeed, but with the head lower than the surface. A small proportion of saline matter was discovered by M. Fourcroy, but scarcely 1/130 part of the whole; and it consisted of phosphat of lime, of soda, and ammonia. In other respects the brain seemed essentially to differ from the other solid parts. It cer-tainly contained little animal matter, and consisted chiefly of albumen; but the latter differed from that of the human body in general, or was changed in its properties by the mixture of another substance, whose nature has not been ascertained. It certainly is not an oily matter, and the brain is not a saponaceous substance. We strongly suspect that it contains sulphur; but much room remains for further investigation. M. Thouret considers it as analogous to spermaceti; and it is singular that, when kept from the air, it for a long time experiences little change.