pedicle from which hangs a vegetable Pitcher, filled with limpid water; and the mouth of this natural amphora is furnished with a membranaceous lid or calyptra, opening on one side! Some writers have fancifully imagined that a vegetable compass exists. in the structure of the concentric layers in the horizontal section of the trunks of trees. It has been urged that these do not strictly conform to the axis, the excess being attributed, to the greater action of the sun on that part of the trunk which faces the meridian. This effect has been thought

to be sufficiently striking and uniform to serve as a sort of compass,
by which the bewildered traveller might safely steer his course, even
in the recesses of the most extensive forest. But if this were the fact,
it would certainly prove to be one of the most incommodious compasses,
that ever was invented. For if the traveller must undergo the labour
of cutting down a tree every time that he may want to know his
bearings, it is to be believed that he will soon become tired of his
instrument of observation. Vol. I.
p. 330.

Du Hamel has shewn that this fancied meridional law has no existence in fact, but that the eccentricity of the ligneous layers in the trunk, depends upon the position of the branches, and of the leading roots, the excess being always on that side in which the most nourishment is derived. Possibly a more decisive indication of the South may be derived from the aspect of a field of ripened corn. Bonnet has remarked that when the swollen grain bows down the stem, the inclination is not accidental, but is more or less directed to the South.

One more quotation shall close our allusions to the analogies which subsists between the inventions of man, and the phenomena spontaneously exhibited by the vegetable tribe. It relates to the possibility of forming a Floral Calendar, by observing the precise season at which certain changes take place in indi 'vidual species of plants. This idea was suggested by Linnæus; but we fully agree with Mr. Keith, that (however, curious these facts may be, in a philosophical point of view) a nation must be in a very low state of refinement which has not better methods of regulating the operations dependant, upon the progress of the seasons. He sensibly remarks,

Although all plants produce their leaves, flower and fruit annually, yet they do not produce them at the same period or season..... But a great many circumstances will always concur to render the time of the unfolding of the leaves somewhat irregular... Linnæus, who instituted some observations on the subject about the year 1750, with a view chiefly to ascertain the time proper for the sowing of Barley int Sweden, regarded the leafing of the Birch tree as being the best indication for that grain, and recommended the institution of similar en observations with respect to other sorts of grain, upon the ground of its great importance to the husbandman. But, however plausible... the rule thus suggested may be in appearance, and however pleasing:

it may be in contemplation. it is not likely that it will be ever mach attended to by the husbandman; because nature has furnished him with indications that are still more obvious, in the evidence of his own feelings, as well as perhaps more correct; as all trees of the same species do not come into leaf precisely at the same time, and as the weather may yet alter after the most promising indications..... The flowering of the plant, like the leafing, seems to depend upon the degree of temperature induced by the returning spring, as the flowers are also protruded pretty regularly at the same successive periods of the season..... Plants exhibit as much diversity in the warmth and length of time necessary to mature their fruit, as in their frondescence and flowering... Such are the primary facts on which a Calendarium Flora should be founded. They have not hitherto been very mi. nutely attended to by botanists; and perhaps their importance is not quite so much as has generally been supposed; but they are at any rate sufficiently striking to have attracted the notice even of savages. Some tribes of American Indians act upon the very principle sug. gested by Linnæus, and plant their corn when the wild Plum blooms, or when the leaves of the Oak are about as large as a squirrel's ears. The names of some of their months are also designated from the state of vegetation. One is called the budding month, and another the flowering month; one the Strawberry month, and another the Mulberry month; and the autumn is designated by a term signifying the fall of the leaf. So that the French revolutionists were anticipated, even by the Indians, in their new names for months and seasons.' II. pp. 449-453.

(To be concluded in our next Number.)

Art. VI. An Essay on the Chemical History and Medical Treatment of Calculous Disorders. By Alexander Marcet, M. D. F.R.S. &c. &c. pp. 181. London. 1817.

THE

HE theory of calculary concretions constitutes a subject as well of philosophical curiosity as professional interest; and as such, may with propriety become a topic of our investigation. It is indeed right that inquiries of this nature should be made in some measure general, were it only that the circulation of knowledge among the profane and uninitiated, is calculated to keep the profession from indulging an indolent satisfaction with that kind and measure of science which has been acquired during the years of probationary studies. This feeling, although far from being universal, is, we fear, by no means very uncommon; and it would probably be more prevalent and operative than it actually is, were it not that the ignorant practitioner runs the risk of having his lack of information detected by his better informed and more inquisitive patient. We would ever deprecate unprofessional interference with practical medicine, an art which can only be taught and acquired in the school of actual experience; but in the view we have just taken of the question, it is perhaps as well that the intelligent portion of the public should gain a little insight into the laws of living existence. Were it

desirable, it would not be practicable, to extinguish the spirit of inquiry that has gone abroad, and all that the medical man, who objects to popular instruction, can do in his own defence, is to take care that he himself be well armed at every point of the medical compass.

The questions which obviously present themselves, as directly involved in the subject of the work before us, are, first, Is an actual existence, to be attributed to the stone or gravel Secondly, What is the precise nature or chemical qualities of these extraneous substances? Thirdly, In what manner are they produced? And lastly, To what extent, and in what way, is medicine operative either upon the concretions themselves, or upon the complaints they produce?

The symptoms by which the presence of a calculous concretion in any part of the urinary organs is indicated, must, in some measure, vary, both according to the nature, size, and form of the concretion itself, and according to the particular part in which it is lodged. The bladder is, however, the most usual organ in which these substances are found, and in that case, the signs denoting its existence are, for the most part, sufficiently unequivocal. It is one remarkable circumstance connected with calculous complaints, that they are, for the most part, accompanied by less derangement in the general health than is produced by the same quantity of local irritation occasioned by other causes. This mark of distinction is especially dwelt upon by Dr. Heberden, and it is of much use to recollect it when either the practitioner or the sufferer feels any hesitation in deciding upon the precise nature of the disordered state. Into the several symptoms which the stone and gravel produce, we refrain from entering further; our object relates rather to the physiological and pathological, than to the surgical part of the investigation.

What then are the constituent principles and chemical com position of those concretions that are so often found in the urinary organs and neighbouring parts of the body? Since chemistry has been so successfully applied to the purpose of ascertaining the nature and qualities of animal secretions, the urine, of course, as one of the most remarkable of these secretions, and as one which undergoes considerable alteration in several morbid states, has more especially excited the attention of the animochemical philosopher. In determining how far the morbid concretions, which constitute stone and gravel, answer in their qualities and ingredients to the matter from which they have beep usually regarded as precipitates, the composition of the fluid in its healthy state becomes a matter of particular interest. Ac-. cording to the most modern and accurate analysis, it is constituted of water, acetic acid, phosphate of lime, phosphate of

magnesia, carbonic acid, carbonate of lime, uric or lithic acid, rosacic acid, benzoic acid, albumen, urea, resin, muriate of soda, phosphate of soda, phosphate of ammonia, muriate of ammonia, and sulphur. In the enumeration of the above ingredients, it will be seen that four of them are marked with italic characters, and they are thus designated, inasmuch as urinary calculi, though possessing a great diversity of essence and character, are, for the most part, more prominently marked by one or other of the above principles. The following is a division of these concretions, which was proposed some time since by Dr. Wollaston, to whom our present Author, Dr. Marcet, acknowledges bimself to be very greatly indebted. 1st. Scheelian, uric, or lithic calculi, composed of uric oxyd, or urate of ammonia. 2d. Fusible calculi, made up principally of the phosphate of lime, and the triple phosphate of magnesia and ammonia. 3d. Boneearth calculi, which are formed almost exclusively of phosphate of lime. To these, the most commonly observed calculi, Dr. W. adds the mulberry calculus, so named from its fancied resemblance to that fruit, and which calculus is a compound mainly of oxalate of lime. Dr. Monro, jun. has divided these substances into five classes; the first including those that are chiefly formed of uric acid and urate of ammonia; the second such as consist of the phosphate of lime and the phosphate of ammonia and magnesia; the third (or mulberry calculus) composed of oxalate of lime and silica; the fourth containing a portion of urate of ammonia; and the fifth, including such as are constituted, for the most part, of a substance which has been named the cystic oxyd. The following is the account, which Dr. Marcet gives of the several kinds and species of these concretions.

The substances hitherto discovered in urinary calculi, by the la bours of chemical philosophy, are as follows. Lithic or uric acid, phosphate of lime, ammoniaco-magnesian phosphate, Oxalat of lime, Cystic oxyd. To which enumeration may be added a vari able proportion of animal matter, connecting and cementing the other ingredients. It very seldom happens that these substances exist singly, and in a state of perfect purity in urinary concretions; yet some of them generally prevail in a sufficient degree to impart to the calculi a peculiar character. And when the mixture is such as to preclude the appearance of any characteristic form, I would, in com. pliance with Dr. Henry's suggestion, assume, this circumstance as the distinguishing quality of an additional species of urinary concre tions Upon the whole, therefore, the different kinds of urinary cal culi may be arranged under the following heads, viz. The lithic calculus. 2d. The bone-earth calculus, paincipally consisting of phos phate of lime. 3d The ammoniaco-magnesian phosphate, or calculus in which this triple salt obviously prevails." 4th. The fusible calculus, consisting of a mixture of the two former. 5th. The mulberry calculus, or oxalat of lime. 5th. The cystic calculus, consisting of

the substance, called by Dr. Wollaston cystic oxyd. 7th. The alter. "nating calculus, or concretion composed of two or more different species, arranged in alternate layers. 8th. The compound calculus, the ingredients of which are so intimately mixed, as not to be separable without chemical analysis. 9th. Calculus, from the prostate gland,'

The lithic calculi and the earthy phosphates, are, as we have ahove hinted, the most commonly found; and next to these, in frequency, are the mulberry calculi, which are easily known by their blackish colour, and irregular mulberry-like shape. The lithic calculus, which is by far the most frequent of all, has more the appearance of a common stone; it is brown, and smooth, and uniform, and in general has a flattened oval figure, while the earthy phosphates, which comprize the bone earth, the ammoniaco magnesian phosphate, and the fusible calculi, and which are next in frequency of occurrence to the lithic concretions, are more usually found of a greyish white appearance, and of a less compact structure.

It will presently be seen that medicinal substances, which are given with a view to dissolve these concretions, or correct their tendency to increase, have a very different effect, as applied to calculi of different component principles; it consequently becomes an object of solicitude on the part of the medical prescriber, to ascertain the precise nature of the particular substance upon which he is endeavouring to bring his medicines to bear. When the patient discharges gravelly matter or small fragments of stone, these ought therefore to be put to the test of chemical examination; and these tests, in the present improved state of chemical science and manipulations, are managed with much comparative facility. We shall present our readers an abridged account of Dr. Marcet's section on this head. Suppose you have a fragment of stone, which you conceive to be inade up principally of the lithic or uric acid, expose it to the flame of a blow-pipe, it will, if thus formed, immediately blacken, emit a smoke of a strong characteristic odour, and gradually be consumed. Upon another fragment of the same concretion, pour, in a glass vessel, some caustic or pure alkali, and, by the addition of heat, it will dissolve speedily. Lastly, try another particle of lithic calculus with a drop of nitric acid, and upon the application of heat, the lithic acid will disappear. The calculi which are composed of the earthy phosphates, are to be ascertained in the following manner; Pour muriatic acid upon the phosphate of lime calculus, and the concretion will soon be dissolved. It may be identified, too, by its first blackening before the flame of a blow-pipe, and soon afterwards becoming white, but not indicating even a disposition to fusion, unless a very intense heat be applied. The ammoniaco magnesian phosphat is capable of solution in muriatic acid, even with more facility than the VOL. IX. N. S.

Y