ing away very far from the original stock. To the former their seems no limit: but the latter is stopped by the increasing unproductiveness and unhealthiness of the individuals, by the susceptibility to disease, and the tendency to revert to the original type. So that increasing departure requires greatly increasing care; and we do not know that any amount of care and time would be sufficient to produce what might fairly be called a new species. The bringing about any marked change by nature's selection is shown to be very hard of proof, and has opposed to its probability the fact that the members of a species which are most unlike have the greatest tendency to pair and are the most fertile; so that we have here, in addition to the ready reversion of modified breeds to the original stock, a law by which the growth or perpetuation of peculiarities is prevented and a constancy given to the characters of the species. This law is more striking from its contrast with the bar that exists to the pairing of different species and the infertility of hybrids. Within a given range dissimilarity promotes fertility; beyond that range it is incompatible with it.

These and other considerations have always inclined me to the opinion that modifications of animal type, occurring in nature, are more likely to be the result of external influences operating upon successive generations, influencing their development, their growth, and their maturity, than of " natural selection" and struggle for existence." But greater effects of these and other similar agencies must be shown before we ought to admit even the reasonable probability of their power to work out the great changes that have been attributed to them.

In pondering over the definiteness of animal types, so marvellously elaborated from a simple form, their slight variability through long periods, the clear manner in which they, many of them at least, are worked out from one another, and which increasing investigation seems to render more and more apparent, the prospect of proving that they are educed from one another by any of the hitherto supposed processes seems to grow more and more distant, and the feeling arises that there must be some other law at work which has escaped our detection.

We are familiarized with the fact that in the inorganic world combinations take place only in certain definite proportions; for instance, that oxygen unites with nitrogen in one proportion to make nitrous oxide in a second proportion, a multiple of the first to make nitric oxide, and so on to the fifth proportion or multiple, which gives nitric acid, and that between them five several fixed proportions as combinations take place. So that the resultants of these and other similar combinations (the inorganic species, as we may call them) are remarkably constant and fixed in their characters; each has its one form, as in the case of crystal, of chloride of sodium, or sulphate of magnesia, which may be broken down or dissolved, but which cannot be modified or made to approach, still less to pass into, any other form.

May there not be something analogous (some corresponding law of combining proportion) presiding over living matter, educing the various forms, fixing their characters, giving them constancy, in fact evolving and fixing the species and preventing their transmutation.

It will be understood that I am not speaking of the combining proportions of the elements in the several animal tissues, which we know, or have every reason to believe, is as fixed as in ordinary inorganic matter, though the combinations are more complex and the formulæ are, in consequence, harder to work out. I speak now not of this, but of something comparable with this and suggested by this, operating not upon individual particles, but on masses, regulating not the chemical composition and form and feature of the tissues, but the form and features of the animal. As oxygen unites with nitrogen only in the definite multiple proportions represented by the figures 1, 2, 3, 4, 5, and under certain circumstances, producing in each instance a special compound unlike any other and marked off from the nearest approaching compounds by distinctive features, and without any intermediate gradations, so in the animal and vegetable world the combinations requisite for evolving living beings may be regulated in a similar manner, taking place only in certain fixed proportions and under certain circumstances and educing certain definite forms, each of which is unlike any other and is marked off from its nearest approach by clearly distinctive features and without intermediate grada

tions. As each chemical compound (say nitric oxide) remains in its given condition, without change, till circumstances have culminated to favour and induce a change, which then takes place, not by slow gradation, but by sudden start, to some other definite compound (say nitrous or nitric acid), so the several animal forms may remain fixed till the conditions for a change, which conditions may be external to themselves, are complete. Thus the change may take place, and not by slow gradations, but by sudden start, by something resembling a new creation, and their definite and clearly distinct form, or species, is produced. Thus, as complementary and similar to the laws of uniformity in design and variety in detail, we may suppose to work on together the laws of gradation and interruption-by the one the living ladder is shaped and bound together as a whole; by the other the steps are preserved distinct, i. e. the individuality of the species is given and retained.

At any rate, whatever be the law and forces which effect and regulate the evolution of species, they are probably of the same kind as those which are operating in the inorganic world. The orderly and definite manner in which forms and features and specific characters are given and preserved in the one instance may be assumed to be of the same nature as in the other; and we must probably refer the fixed animal and vegetable types to influences identical with, or similar to, those by which the forms are assigned to crystals and the stratification is given to rocks, by which the geological epochs have been determined and the boundaries of our planetary and solar systems have been set. One cannot but think that it may be within the power of man to work out and to comprehend, in some degree at least, the principles by which these breaks in the organic and inorganic works, constituting as they clearly do an important feature in the plan of creation, are brought about and regulated.

The pendulum of opinion on this great question (the question of working by general law, or working by special interferences) may be expected long to swing to and fro ere it rests upon a settled conclusion. In the meantime it will help to keep the wheels of science going and add fresh knowledge to our heap.

And let us not shrink from the free, bold, fair discussion of these and other kindred subjects under an apprehension that they are calculated to lower the religious elements and shake the faith. Such discussions, and the thoughts which give rise to them, are a necessity, an inevitable result of advancing science, which it is as impossible to stop as the progress of time itself; and that which is inevitable must be accepted. Twould show a want of faith to resist it. Knowledge may be man's trial; but that applies to knowledge of all kinds, of that which is esteemed good as well as of that which is esteemed evil. Certainly the fruit of its tree brings responsibility; but responsibility is man's highest dignity, and opens one of the avenues to the tree of life. Theological zeal and scientific zeal are both good, and representatives of good elements in man's nature-the element of faith and the element of thought. Both should cooperate in the work of purifying and elevating the character; indeed the one cannot advance safely without the other. Still they will now and then come into collision and threaten to undermine one another, needing forbearance and discretion to restore their harmony. One cause of the occasional outbursts of the odium theologicum is, I think, due to a fault on the side of the theologians. Not satisfied with, or distrusting the really unassailable position on which their future stands, with its foundations deep laid in man's consciousness and God's work, they have endeavoured to raise outworks on the shifting ground of natural science, by drawing arguments from analogy, by associating special views of creation and resurrection with true religious belief, and by insisting on certain literal interpretations of the physical medium through which spiritual truth has been conveyed to us. Hence each unfolding of the material laws is liable to be regarded with suspicion, lest it should sap the foundations that have been thus unwisely propped. Religious arguments drawn from the physical world are very liable to prove two-edged swords cutting both ways according to the manner in which they are wielded, or staffs that penetrate the hands of those that lean upon them. Theology may rest safe upon her own position, and watch with confidence and satisfaction the advancing waves of science,

feeling assured that, though they may beat at times rather roughly upon her, they will soon calm down under her leavening influence, and simply add too and strengthen her soil.

And we may work patiently on, not pressing hastily to conclusions which our aspirations seem to point to, but relying on careful observation and honest reasoning to give us a solution of some of the great problems which animal life presents.

Letter communicating the result of an application to the General Medical Council as to a Grant for investigating the Physiological Action of Remedies, from Dr. ACLAND.-The application had been refused, on the ground that such investigation was not within the sphere of the Council's duties.

On the Effects of the Pollution of Rivers. By Col. Sir J. E. ALEXANDER.

Remarks on the so-called Cattle-Plague Entozoa. By Dr. COBBOLD, F.R.S. The author pointed out the importance of understanding the precise nature of these bodies. They were not, properly speaking, Entozoa, but were psorospermial sacs of microscopic size. He found them varying from" to a greater length in cattle, and less than" in sheep. They were extremely abundant in the heart. The contents of the sacs displayed a complete cell-formation, the ultimate particles being granular. Each granule or pseudo-navicel, as it might be called, measured only the " in diameter; some were round, others oval, a few reniform. Under very high powers minute refracting points or nucleoli were observable in their interior. Practically, they were harmless and could be swallowed with impunity. (At the Evening Soirée Dr. Cobbold exhibited specimens under the microscope.)

On the Colour of Man. By Dr. J. Davy, F.R.S.

The author first enumerated the various shades of complexion in connexion with the localities in which they are found, and then went into the subject of causation. The warmer the climate, the less the difference of colour of arterial and venous blood. The Esquimaux are neither fair nor dark brown, but intermediate. The long, continuous solar effect for one half the year associates them with the inhabitants of the tropics, whilst their living underground the other half does not favour the depuration of their blood. With regard to the Chinese, he ventured the conjecture that their colour may be owing to an imperfect elimination of bile; that it might become hereditary and pass in course of time into that distinctive of climate. He showed that the circumstances of a cold or temperate climate favour fairness of the skin. Of this he gave a variety of instances; and invited discussion on a subject of no ordinary interest in regard to health and beauty.

On the Question, Is the Carbonate of Lime in the Egg-shell of Birds in a Crystalline or Amorphous State. By JOHN DAVY, M.D., F.R.S., &c.

A high authority in physiology, M. Milne-Edwards, seems to consider it in the former, in a crystalline state: his expression is, that in the enveloping membrane it has a crystalline appearance*. The grounds for this, his opinion, he does not give, nor does he enter into any minute details on the subject.

From such observations as I have made on the egg of the common fowl and on the eggs of other birds, especially of the smaller, I am disposed to the adoption of the opposite conclusion, viz. that the carbonate of lime in the shell is in an amorphous and finely granular state. In this state I have found it in the egg of the common fowl, taken from the oviduct when the carbonate of lime was only sparingly deposited in the investing membrane. Again, in the instances of the eggs of the smaller birds, which are exceedingly thin, are easily crushed and reduced to a fine powder, well fitted for microscopical examination, I have never * He says, "Celle-ci (the shell) est formée par une couche plus ou moins épaisse de cellules vésiculaires dans l'intérieur desquelles du calcaire carbonaté ne tarde pas à se déposer et à prendre une apparence cristalline.”—Tom. viii. part 2, p. 527.

observed any appearance of crystals, only of granules, these of various sizes, the smallest only just within the limits of vision. Further, when I have subjected a minute portion of shell to the blowpipe, and rapidly destroyed by combustion the animal matter, in the residual lime comminuted with a drop of water added to it there has been no appearance immediately of crystals, only of granules: I say immediately, because, after a short exposure to the air, the lime, that which had been deprived of its carbonic acid, reuniting with carbonic acid derived from the atmosphere, then assumed a crystalline form, and presented minute well-defined crystals, chiefly of the cubical kind, and this the more rapidly the more free the exposure, as shown by comparing a portion covered with thin glass and another not so covered. And if no water be used, no solution formed, then no crystals were produced, even when the lime, attracting moisture from the atmosphere, becomes converted into a hydrate*.

That crystallization is of rare occurrence in connexion with organic development is an admitted fact, and where it has been observed, as in the blood, it seems to be yet a problem waiting solution, whether the crystals detected were formed in the living fluid and were a part of it as such, or were formed after privation of life; in other words, whether by a formative process analogous to secretion, or by a destructive process pertaining to excretion. That coagulable lymph or fibrine may lose its vitality whilst in the living blood-vessels, and undergo a softening similar to that which takes place in it out of the body at a certain temperature, is now an established pathological fact; and as blood-corpuscles are always included in the coagulum, these two may be inferred to be in the same category in relation to vitality. Were life and crystallization compatible, might we not expect to find crystals in bones? But I am not aware that they have ever been detected in any bone, however early its examination may have been in the embryo. It may perhaps be said that crystals are frequently met with in calculi. Admitting the fact, is it not more reasonable to refer their formation in these bodies not to vital action, but to the absence of vitality, and to ordinary physical causes, calculi themselves being anorganic, and the result of causes of the same kind, i. e. physical? And here I may mention a fact which I am disposed to view in the same light. I have found in the ovary of a fowl a white opaque matter, resembling in appearance lithate of ammonia, as seen in the urinary excrement of birds; but on examination it proved to be not a lithate of ammonia, but carbonate of lime mixed with animal matter, the former partly granular and partly crystallized, chiefly in minute cubes.

The rapid manner in which the carbonate of lime is deposited on the egg in the oviduct, and always, as it would appear, associated with animal matter, might perhaps be used as an argument against its deposition on the membrane in a crystalline form: be this as it may, both the shortness of time in which the incrustation takes place and the quantity of carbonate of lime which enters into the incrustation is remarkable. A hen, a good layer, in full vigour, commonly lays an egg every day, and I have never found more than one egg in the oviduct at the same time. Of an egg newly laid, which weighed 9069 grs., the entire shell was found to weigh 694 grs., of which, on analysis, 161 grs. proved to be animal matter, 533 grs. carbonate of lime, with a trace of carbonate of magnesia and phosphate of lime; so this large quantity of carbonate of lime must have been poured out from the blood in the short space of twenty-four hours or less!

Another fact I would mention, which also may be adduced in favour of the idea that crystallization is not incompatible with vital action. I refer to the microscopical crystals, chiefly prismatic, which are found to occur in the brain and spinal chord of the frog and toad, and which I have detected also in the newt, and this normally, as far as I am aware, without exception, and, I may add, which occur also in profusion in the retina. From the trial I have made of them, they appear to consist chiefly of phosphate of lime. The existence of these crystals is a fact that does not seem to admit of the same explanation as calculi. It seems altogether exceptional-a problem waiting solution.

In certain vegetables, too, as is well known, crystals have been found in their Hydrate of lime, formed by exposing quicklime to the atmosphere, I have found finely granular and free from crystals.

cells; but it is questionable whether they are anywise essential to the growth and well-being of the plants, and are not rather the results of disease, depending on a state of the fluids, somewhat analogous to that which in animals is favourable to the production of calculi. It would be foreign to my purpose to express any opinion as to the great question whether, in the vital economy, the forces in action are merely physical forces, or, admitting, as must be admitted, that these forces are concerned in the phenomena of life, whether something more is not required, a special force, a vital force, to give them direction, or modify their influence.

Note on an Addition to the Sphygmograph. By Dr. BALTHAZAR W. FOSTER. After describing the construction and application of Marey's Sphygmograph, the author pointed out that the screw regulating the amount of pressure exerted on the artery under examination required adjustment for nearly every case. Too great pressure often materially altered the form of the pulse trace; and as it is essential for accuracy in comparative observations that the pressure on the vessels should be the same, the author stated that by having an index attached to the pressure-screw, and a graduated circle described round the screw as a centre, the position of the index would always enable the observer to exercise the same amount of pressure in any number of cases.

On a Peculiar Change of Colour in a Mulatto. By Dr. BALTHAZAR W. FOSTER. After alluding to the present state of our knowledge of the conditions connected with the development of pigment, the author related an instance in which he had observed a gradual disappearance of the cutaneous pigment in a Mulatto aged 43. Minute white spots first appeared on the man's back, and by coalescing gradually formed large white patches. These constantly extending, in the course of six years the whole of the trunk became perfectly white, spots of the original colour remaining only on the extremities. The face retained its dark hue, and an irregular margin encircling the neck formed the limit of the upward advance of the white colour. Isolated spots of white had appeared, however, on the forehead and at the angles of the jaw. The white skin was perfectly healthy in appearance and not to be distinguished from that of a European. The man's hair was black and crispy, and of a flattened elliptical form on section. Blisters applied to the bleached surface restored the dark colour in irregular spots, which remained unchanged for several months. No discoverable condition in the man's constitution or habits could be regarded as the antecedent of the remarkable change, except possibly a very weak and sluggish state of the circulation. A series of large photographs illustrated the communication.

On the Action of Carbonic Oxide on the Blood. By Dr. A. GAMGEE. When carbonic oxide is passed through venous blood it acquires a persistently florid colour, which was first pointed out by Claude Bernard, and the colouringmatter, although it possesses a spectrum identical with that of ordinary blood, is distinguished from it by not yielding, when treated with reducing agents, the spectrum first described by Stokes as that of reduced or purple cruorine. This property of carbonic-oxide blood was first published by Hoppe. As a result of his own investigations, Dr. Gamgee has found:-First, that the peculiar compound of carbonic oxide and blood colouring-matter is formed even when the latter has been reduced, and is still in the presence of a large excess of a reducing solution. Secondly, that when the compound of carbonic oxide and colouring-matter is treated with acetic acid, whilst hæmatine is formed, carbonic oxide is disengaged. Thirdly, that carbonic oxide, besides modifying the optical properties of the colouring-matter of blood, affects in a remarkable manner the point at which it coagulates, so that, under its influence, an almost perfect separation of the hæmotoglobulin (using the term to express the normal colouring-matter of the blood) from the albumen may be effected. Normal ox's-blood, when diluted with nine times its volume of water, becomes turbid at 145° Fahr., and when the temperature has reached 172° Fahr. its colour is completely destroyed. If such a