trisnitrate of bismuth, passed into the milk of asses." (p. 638.) Mercury probably does the same, judging from the effect of the medicine upon syphilitic infants when administered to their nurses.

The tenth chapter is devoted to the Locomotive Apparatus.

Bone. The composition of the bones varies with the different parts of the body from which they are taken. The proportion of animal matters to the earthy may be stated in round numbers as 2 to 3. Their constituents in the human subject are gelatin, (or a tissue which when boiled furnishes this principle,) phosphate and carbonate of lime, phosphates of magnesia, soda, and chloride of sodium. Fluoride of calcium has been mentioned among the constituents of the bones, but Dr. Rees has shown that it admits of considerable doubt whether it really does exist in them. The bones have been subjected to analysis in various diseases. In caries and necrosis no chemical alteration has been detected. In rickets and mollities ossium the proportion of earthy matters has been found so much reduced as to bear to the animal matters the ratio of only 1 to 3, and the proportion of phosphate of lime diminishes in somewhat greater proportion than that of the other saline components. Permanent callus differs little in composition from ordinary bone; when first deposited, the organic compounds predominate, and the phosphate of lime bears a smaller ratio to the other salts than in healthy bone. The teeth are more compact than ordinary bone, and contain about 3-10ths of organic matter. They are occasionally encrusted with a calcareous deposit, known as the tartar of the teeth, consisting of about 80 per cent. of phosphates of lime, and the remainder of mucus and the constituents of the saliva.

Little of interest is known respecting the changes which the muscular system undergoes. Fibrin forms the essential ingredient in its composition, but in certain degenerations of the tissue we find the true muscular fibre replaced by a peculiar saponifiable fat, the nature of which has not been accurately ascertained. In a few instances the texture has been found ossified and composed of the same ingredients as healthy bone. The aponeurotic, tendinous, and ligamentous tissues contain, besides albumen, a considerable proportion of matter convertible by boiling into gelatin; but this principle does not appear to exist ready formed in them. The concluding chapter of the work is devoted to Morbid Products. False membrane. The principal ingredients in this are albumen, in its coagulated and uncoagulated form, and fibrin. In one instance, analysed by L'Heritier, cholesterin was found to be present.

Pus. This product, when healthy, has a specific gravity of 1031 to 1033. It is generally neutral to litmus; by exposure to air, it soon undergoes decomposition. It varies greatly in appearance with the nature of the surface from which it is secreted. Nothing definite respecting the chemical differences presented by these varieties is known. Pus has been found by analysis to contain albumen, lactates, chloride of sodium, phosphate of lime, with a small quantity of iron. Respecting its microscopic appearance, we have nothing to add to the quotation already made when speaking of its occurrence in the urine. Treated with ether, pus gives up a certain proportion of fatty matter, by which Rayer proposes to distinguish it from mucus; but this is a vague and uncertain character, as fat may find its way into the different secretions from other sources than the formation of pus, and Dr. Bird found only 0.5 per cent. of fat

in pus which he analysed from a psoas abscess. Our author seems to favour the exploded doctrine of a resolution of certain parts of the solids into pus, and we shall therefore not be surprised to find his ideas on its formation rather hazy and ill developed.

Tubercles. After successfully refuting, both on chemical and physical grounds, the hypothesis of Lallemand and Cruveilhier, that tubercles arise from concrete pus, he furnishes us with the following excellent specimen of the art of wrapping up ignorance in the garb of science, and passing it off upon the unwary under the guise of sterling knowledge:

"It is with tuberculous matter as with pus. It is a heterogeneous product, capable, in my opinion, of developing itself under the influence of a variety of causes whenever the tuberculous diathesis exists. Like pus it may proceed from metamorphosed blood; like it also it may consist in the transformation of a normal or abnormal tissue.

"In all these cases the formation of tuberculous matter depends upon the inability of the tissue to assimilate, that is to say, to convert into its normal substance the materials brought for its nutrition; whether because the materials resist the transformation, or because the assimilating power of the tissue cannot exert itself with sufficient energy to master the material to be assimilated. The principal cause depends either upon the plastic activity in general being altered from its normal conditions, upon the formation of the blood remaining incomplete, or else upon the degeneration of this fluid." (p. 680.)

Vogel gives the following account of the microscopic examination of tubercular matter. After directing a thin slice to be placed under the

object glass, he says

"We see now in the proper substance of the tubercle absolutely no blood-vessels, and convince ourselves by repeated examinations of such fresh sections, that the substance of the tubercle itself not only contains no blood-vessels, but that by its deposition in the pulmonary tissue the original vessels of the lungs have been compressed and obstructed. We discover, on the other hand, the serpentine fibrous bundles of the substance of the lungs forming meshes, and still entirely unaltered between the masses of tubercle. If, concealed by masses of tubercle they do not at once appear evident, they will do so on adding ammonia, which renders the substance of the tubercle transparent. If we examine the substance of the tubercle more accurately, by washing with water, rubbing it down, tearing it with needles, and so forth, and seek to resolve a fine section into its morphological elements, we shall convince ourselves that it consists entirely of an aggregation of the tubercle-cells already mentioned, without any connecting medium." (Vogel, p. 458.)

These cells are thus described:

"In different cases of tubercular disease, and even commonly upon the same spot of the same tubercle, the cells exhibit great differences. Sometimes they are small, only from 1-200 to 1-400 of a line in diameter, for the most part roundish, with pale outlines; their nuclei are proportionately large, from 1-300 to 1-500 of a line in diameter, and are commonly roundish, rather dark, with or without nucleoli; they fill up almost the whole cell, which contains no solid particles beside the nucleus; in other cases the cells are larger, 1-80 to 1-200 of a line in diameter, sometimes roundish, sometimes oval, at others of irregular form, elongated or drawn out into a tail; their nuclei are smaller in proportion to the size of the cell, and occupy only a third or fourth part of its capacity. These cells, besides their nuclei, often contain small globules of fat, in greater or less number..... In other cases the cells contain granules of a black pigment.

"We find that the tissue of the lungs infiltrated with tuberculous matter, passes quite gradually into the healthy tissue, and in the former we never find anything resembling a membrane inclosing the tubercle. The surrounding pulmo

nary tissue appears sometimes normal, sometimes filled with nucleated cells, a consequence of the inflammation excited by the pressure of the tuberculous mass upon the neighbouring parts." (Ib. p. 457-9,)

The principal chemical constituent of tuberculous, like that of all malignant deposits, is albumen; and in addition, gelatin, fibrin, fatty matters, phosphate and carbonate of lime are enumerated. In hardened tubercles, L'Heritier found 5 to 9 per cent. of animal matters, and from 91 to 95 of a mixture of carbonate and phosphate of lime.

In colloid matter gelatin is said to preponderate.

The encephaloid, or medullary tumour, appears to contain, besides albumen and fibrin, gelatin, phosphorized fat, and occasionally cholesterin, besides saline matters. The deposit in melanosis consists principally of albuminous and fibrous matter, with a variable proportion of fat, coloured with an organic substance, soluble in dilute sulphuric acid, and resembling in everything but its colour the hematosin of the blood. Phosphate of lime and iron are found among the saline ingredients. Except in the absence of the colouring matter, and in the variation of the proportions of its constituents, which here, as well as in melanosis, vary greatly, the matter of scirrhus differs little in composition from that of the last-named disease.

Calculous concretions. These occur in various parts of the body, and as they are derived from the deposition of sparingly soluble compounds contained in the different fluids, they naturally vary with the situation in which they occur, and the composition of the secretions from which they are separated. Under the prepuce, concretions have been found, consisting of phosphate of lime, mucus, and fatty matter. From the tonsils, larynx, nose, salivary, lacrymal, and pancreatic ducts, and bronchi, calculi have been taken, consisting of carbonates and phosphates of lime and magnesia, mucus, and fatty matter. The proportions of these vary greatly, and the magnesia is always small in quantity. Arthritic calculi, besides phosphate of lime, generally furnish a considerable proportion of the urates of soda and lime.

Intestinal calculi our author divides into three classes, according to their origin:

"Ist. Those which originate in nuclei formed either in the alimentary canal or biliary apparatus, but which are covered with saline particles or animal matters during their passage through the intestines: 2dly, those which originate in nuclei composed by foreign bodies, such as seeds, stones of fruit, the husks of fruits, fragments of bones, &c, covered with crystalline particles which would not have become aggregated but for the presence of these foreign bodies; and 3dly, those which are entirely formed in the digestive tube which are homogenous, and present no distinct nuclei. It is not very rare to find in the alimentary canal, and more particularly in the large intestine, concretions entirely different from those of which I have just spoken. Some are concreted masses ordinarily derived from three sources: 1st, A morbid state of the secretions poured into the digestive tube or secreted upon its surface; 2dly, an alteration of the fecal matters which occasionally become charged with earthy particles during their retention in the cæcum and in the large intestine; and 3dly, the introduction into the stomach of substances not susceptible of digestion. Others are of a fatty or adipocirous nature." (p. 695-7.)

Biliary calculi. These also consist of three principal varieties :—the lamellated, which are hard and but slightly inflammable; the radiated, or striated, which bear a crystalline semi-transparent appearance, and

often a granular surface,-they consist of cholesterin nearly pure; and the corticated, consisting of a lamellated nucleus of cholesterin, enveloped by an intermediate layer, over which is a crust or bark of infusible matter. Besides cholesterin, which is the principal ingredient of most. biliary calculi, the following substances have been met with: The yellow and green colouring matter of bile, picromel (or bilin), mucus, albumen (?), carbonaceous matter, carbonates of lime and soda, phosphates of lime and magnesia, and oxide of iron.

Our author concludes his treatise with a brief summary of the most important facts relative to urinary calculi. A neat sketch of the methods of detecting the presence of the different ingredients is given; and a few pages are devoted to the chemical treatment of calculous disorders, in which considerable stress is laid upon the method of treatment by alkalies. The expectations of success held out are considerably more sanguine than we are warranted in forming from experience.

In conclusion, we may safely recommend the treatise of M. L'Heritier, as a valuable aid in the study of chemical pathology. Although he is apt to be prolix in unimportant matters, and to subdivide his subjects to excess, his work will be found a judicious compilation of most that has been done upon the subject, and we have pleasure in adding that the writer appears to have studied with care the researches of foreigners as well as those of his own countrymen, though he has not always been sufficiently careful in stating the source whence his information is derived : he has at the same time added many valuable analyses and observations of his own. The work is, however, deficient in the terseness, close reasoning, and laborious accumulation of facts which distinguish that of Lehmann; and in the novelty and originality of investigation which mark the treatise of Vogel.

From the review we have just taken of one of the most recent treatises on pathological chemistry, we see how vague and incomplete our knowledge is upon almost every part of this important branch of science. We are as yet but just entering upon its study. Great difficulties in its prosecution have still to be overcome. These arise in part from our ignorance, in part from the very nature of the subject itself. In no department of inquiry is a more scrupulous attention to literal accuracy necessary, inasmuch as the observations and analyses being made upon peculiar and individual cases are not susceptible of the severe verification and close scrutiny by other observers, which researches in many other departments of science admit, and from which we derive such a feeling of exactness and certainty in the deductions obtained. Speculations of high interest have been thrown out; the field of investigation is new; many ardent inquirers have entered upon it, eager to obtain a reputation where labour and accuracy are alone needed to ensure a creditable station. The labour is willingly given, but the accuracy which alone can render that labour valuable, has too often been forgotten or neglected, either from the inadequacy of those who have undertaken the task to execute it satisfactorily or, what is still less excusable,-from indolence or over-hastiness, and consequent omission of the needful precautions. Great, howevereven in this early stage, and notwithstanding our comparative ignoranceare the benefits that have accrued to the science of medicine from the

prosecution of Pathological Chemistry; and proportionately great, therefore, is the encouragement we may derive for its further cultivation; as it is impossible to doubt that increased knowledge will add to the precision and fitness of our remedial measures, as well as to the accuracy of that upon which all treatment must be based, our diagnosis of disease. The researches of the present day seem all converging towards one point, viz. the mutual convertibility of the various species of force; rendering it probable that the amount of force existing on our planet is as definite as that of matter itself. The leading idea in Liebig's treatise is the dependence of all manifestations of vitality upon a definite and corresponding amount of chemical force; an idea at present wrought out, it is true, but imperfectly, and often supported by this ingenious philosopher rather by sweeping analogies and bold speculation than by sober experiment and careful observation: but the general correspondence of facts with the theory recommends it strongly to our notice, and the simplicity and beauty of the hypothesis almost irresistibly leads the judgment captive. The close mutual dependence of the forces of electricity and magnetism is now established beyond the shadow of a doubt; a connexion so intimate that a correct estimate of the amount of the one forms the most accurate measure of the quantity of the other,—a connexion so intimate that from the same source we may at pleasure obtain either, and when obtained, we may, by a slight modification of our arrangements, convert the one into the other, as is strikingly exemplified in that invaluable instrument the galvanometer.

Not less closely related to electricity and magnetism is the equally subtle and important agency of heat. The researches of Melloni, who, in the beautiful thermomultiplier devised by Nobili and himself, applied Seebeck's discovery of thermo-electricity to the investigation of the laws of radiant heat, have shown that the deviation of the magnetic needle, produced by an electric current excited by the rays of heat falling upon the exposed surface of the multiplier, may be employed as an accurate measure of the quantity of heat which falls upon the instrument at any given moment; and we are all familiar with the converse of the fact in the intense evolution of heat produced during the passage of electricity through imperfect conductors, a property of which the chemist avails himself to fuse the most refractory substances in nature, and which may, under due regulation, as in Snow Harris's experiments, be employed as an exact measure of the force in circulation. Faraday has taught us that we may convert a given amount of electric action into a chemical action equally definite in quantity, and, vice versa, that chemical action may be made to produce a corresponding and equivalent development of electricity, and if of electricity, an equivalent amount also of magnetism and of heat. Indeed, the definite quantity of heat, disengaged by chemical action, has been ascertained by direct experiment, independent of the electricity set free, and to chemical action we ordinarily have recourse for the production of artificial heat.

Here are four of the subtlest agents of the material universe related by the closest ties. The measure of the one becomes a measure of each of the others, and doubtless, could we make the suitable arrangements, we should always find one force associated with a corresponding amount of each of the others. They appear not to be independent forces, each