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and form a full volume. The general aspect of the progress of discovery as exhibited in these records is such as to excite much interest; and the Royal Society under its new President seems to be continuing its labours in a degree fully equal to the diligence and success displayed at any former period. We have already noticed one set of very important discoveries, which greatly add to the high distinction already attending the name of Davy, and mark the present volume of the Transactions with peculiar interest. In relation to this subject, we may observe that this volume contains a notice, stating, that the President and Council adjudged the medal on Sir Godfrey Copley's donation for the year 1820, to Professor John Christian Ersted, of Copenhagen, for his electro-magnetic discoveries; and it would have added greatly to the value and interest of the volume, had it been enriched by an account of that philosopher's discoveries.
As we have already occupied some space in our late numbers in the examination of some parts of the volume before : us, we propose at present, briefly to enumerate the subjects of the several papers under their respective departments ; going more into detail with those of more peculiar importance, beginning with the departments of physiology and chemistry.
On subjects of anatomy, physiology and natural history, we have many able papers to present to the notice of our readers.
No. 1. On the black rete Mucosum of the Negro, being a defence against the scorching effects of the sun's rays. By Sir Everard Home, Bart. F.R.S.
This paper contains some simple experiments made by comparing the effect of heat radiating from the sun, in producing the sensation of scorching, with that of heat intercepted by an absorbing substance.
In one instance a thermometer placed on the naked hand, rose to 98° in the sun, and a scorching pain was experienced ; whilst on the other band a thermometer placed under a piece of black cloth, rose to 106° without the slightest pain ensuing.
A negro's hand exposed to a temperature of 100° in the sun for ten minutes felt no pain whatever.
Several other experiments of a similar nature were made, from all which Sir E. Home deduces the following conclusion.
“ From these experiments, it is evident that the power of the sun's rays to scorch the skin of animals is destroyed when applied to a black surface, although the absolute heat, in consequence of the absorption of the rays is greater.
& “ The same wise providence which has given so extraordinary a provision to the negro for the defence of his skin, while living within the tropics, has extended it to the bottom of the eye, which would suffer in a greater or less degree when exposed to strong light; the retina, from its transparency allowing it to pass without injury. The nigrum pigmentum is not necessary for vision, but is provided only as a defence against strong light.'
Several instances are mentioned in support of the last assertion. Among them we learn that the owl, which never sees the sun, has no nigrum pigmentum; in Negroes it is darker than in Europeans; and in animals exposed to the šun, darker than in those not so exposed.
The author concludes by saying tbat he bas merely stated facts; but that Sir H. Davy explained them by saying that the radiant heat in the sun's rays was absorbed by the black surface, and converted into sensible heat. A distinction of considerable importance in studying the nature of heat; it being found to possess different properties when (if we may be allowed the expression) at rest, and when in motion.
Nos. 2 and 3, are short notices of a singular fact in natural history.
No. 8, is by Dr. J. Davy, on some points in the physiology of the genus Rana.
No. 5. The Croonian lecture. Microscopical observations on the following subjects. On the Brain and Nerves ; showing that the materials of which they are composed exist in the blood. On the discovery of valves in the branches of the vas breve lying between the villous and muscular coats of the stomach. On the structure of the Spleen. By Sir Everard Home, Bart., V.P.R.S.
The information which Sir E. Home has been enabled to obtain on these subjects is owing to the great perfection to which microscopical observation has been carried by Mr. Bauer. The most important feature of these discoveries, consists in the knowledge obtained of the existence of a transparent elastic mucus, soluble in water; which serves to unite in rows small colourless globules, from co to o6o part of an inch in diameter : thus forming them into fibres: bundles of these fibres constitute the structure of the nerves, and the brain is found to contain the same globules united by the elastic mucus. The transparency and solubility of this mucus, Sir E. Home thinks will account for its not having been bitherto noticed. There is found to be some difference in the prevalent size of the globules in the different parts of the brain. In general terms it may be said that the smaller sized globules prevail most in the outer parts of the brain, and the larger in the interior. The proportion also of the mucus to the quantity of globules, is greater, and its consistence less tenacious in the outward or cortical part of the brain, than in the medullary or inward part.
Every part of the brain is supplied with minute blood vessels. These are found traversing, the cortical part in very delicate ramifications. In the medullary substance they are larger. The veins are of smaller diameter than the arteries, and are furnished with numerous valves. This circumstance, Sir E. Home thinks, explains why there are no absorbents in this organ: these veins perform that office by means of their valves ; and carry the absorbed matter into the superior longitudinal sinus ; which seems to be more of a reservoir than a vein, and is found to contain decomposed colouring matter besides blood.
These investigations are intermixed with some very hypo. thetical considerations which we will not notice, but proceed to mention the progress of these researches, in tracing the presence of the soluble transparent mucus through all the brain and nerves as the medium by which the globules are connected together; and lastly the same substance was found to be an important constituent in the blood, and the medium by which the colouring matter is attached to the surface of the red globules. Thus terminates the first object of these enquiries. The second was one in some measure connected with the first, having been suggested by the discovery of the absorbent system of the brain, wbich led Sir E. Home to conjecture that there might be some similar provision for carrying off the fluids taken into the stomach whenever the quantity or quality interfered with the process of digestion, . He had ascertained that some fluids were so carried off ; and by Mr. Bauer's means he was enabled to demonstrate vessels in the coats of the stomach, and to give strong collateral evidence of their acting as absorbents. And it inmediately suggested itself that this was the use of the branches of the vas breve in a situation well supplied with other blood vessels. Into the detail of the investigation we cannot enter, as they cannot be understood without the beautiful plates which acompany the paper. A similar remark will apply to the author's examination of the spleen; of which we will only give the concluding inference:
“ The spleen from this mechanism appears to be a reservoir for the superabundant serum, lymph globules, soluble mucus, and colouring matter, carried into the circulation immediately after the process of digestion is completed."
No. 12. A further account of fossil bones discovered in caverns inclosed in the lime stone stocks at Plymouth. By Josepb Whidbey, Esq.
Sir E. Home has added an anatomical description of the different bones, &c.
No. 18. (Part II.) An account of the skeletons of the Dugong, two-horned Rhinoceros, and Tapir of Sumatra, sent to England by Sir Thomas Stamford Raffles, Governor of Bencoolen. By Sir Everard Home, Bart. V.P.R.S.
This paper is for the most part confined to anatomical details. We will only extract one part, which is interesting, as shewing several beautiful instances of provision for the habits and functions of the animal, in its structure.
The bones of the skeleton give a form very different from what is met with in the whale tribe. The middle part of the back is the highest point in the water: and the lungs are extended to great length on the two sides, close to the spine, so that they furnish the means of the animal becoming buoyant, and when no exertion is made, the body will naturally float in an horizontal posture.
When we consider that this animal is the only one yet known, that grazes at the bottom of the sea, (if the expression may be allowed,) and is not supported on four legs, we must admit that it will require a particular mode of balancing its body over the weeds upon which it feeds.
The Hippopotamus which uses the same kind of food, supports itself under water by the strength of its limbs; and the Dugong, as a compensation for not being able to support its body on the ground, (having only two short arms or fins,) has this means of suspending itself in the sea, peculiar to itself. The peculiarity of its position explains the form of the jaws, which are bent down at an angle with the skull, this new mode of floating, when compared with that of other sea animals, makes a beautiful variety. The Balæna Mysticetus, which catches its prey at great depths, is surrounded by blubber, not unlike a cork jacket. The Spermaceti Whale, whose prey is not so far removed from the surface, has the mass of spermaceti in a bony concavity on the skull. The shark has the liver loaded with oil, nearly in the same relative situation as the lungs of the Dugong.
The rest of the paper consists of anatomical descriptions of the Rhinoceros and Tapir. The whole is illustrated by several plates of the Dugong and the other animals, as also of their skeletons and various parts of their anatomy, for the original specimens of which we are indebted to the industry, and zeal in collecting subjects of natural history, which are so conspicuous in Sir T. S. Raffles.
No. 21. Is entirely of a surgical nature: detailing the case of a very elaborate and skilfal operation, performed by Mr. Earle, by which a portion of the urethra, which had been destroyed, was replaced by a canal, formed by gradually supplying the deficiency, by portions of the adjacent integuments.
No. 26. On the peculiarities that distinguish the Manatee of the West Indies, from the Dugong of the East Indian seas. By Sir Everard Home, Bart. V.P.R.S.
The Manatee differs in its external form from the Dugong, the tail being much broader, and the ribs having greater lateral extension. As this animal feeds upon the plants that grow at the mouths of great rivers, and the Dugong upon those met with in the shallows of the sea, this difference of form will make it more buoyant, and better fitted to float in fresh water : while its habits of life place it between the Dugong and Hippopotamus. The account is illustrated with plates.
No. 28. On the Nerves: giving an account of some experiments on their structure and functions, which lead to a new arrangement of the system. By Charles Bell, Esq.
This is an elaborate and interesting paper, on a branch of physiological science, the most important, and at the same time hitherto the most obscure, but which the author of these researches conceives has now assumed a new character: the intricacies of the nervous system have been unravelled, and the peculiar structure and functions of the individual nerves ascertained; so that the absolute confusion in which this department was involved, has disappeared, and the natural and simple order has been discovered. Such at least is the view which Mr. Bell takes of the subject in its present improved state; the advancement having been occasioned by the gradual accumulation of observations within the last few years, among which his own hold a very conspicuous place.
The great principle which Mr. Bell has the merit of suggesting, is, that where any organ performs several functions, it is supplied with as many separate systems of nerves as it performs offices : and that the same observation may be extended to many muscles and other parts of the body, which though not the direct organs of a particular function, are yet called into action, whenever that function is exercised, as auxiliaries. In this way, many of the most remote muscles are employed, though perhaps hardly perceptible, in many functions of an organ, which seems not at all connected with them.
" When," says the author, " we minutely and carefully examine