and the application of heat, when the bright reddish colour immediately produced shows its presence. The diurnal per centage of sugar must be told by the specific gravity, or by Soleil's method of the rotation of the plane of polarization, or by what Valentin recommends after Fehling-dropping the urine into a solution of sulphate of copper, with tartrate of potassa and soda of a known strength, till no red precipitate any longer forms. A little pure nitric acid added to the urine in a watch-glass, shows by its crystallization the presence of an excess of urea, and of a too rapid oxidation and disintegration of the body. A minute portion of blood in urine becomes evident by its change of colour on the application of heat, and by a degree of coagulation. If nitric acid produces a brown deposit in urine, it is uric acid. If the urine contains an excess of colouring matter a few drops of hydrochloric acid will probably change it to dark red or purple. In the above cases the urine is supposed to be clear and acid. If it is alkaline and has a sediment, add a little nitric acid, and if a white sediment still occurs it is albumen; if brisk effervescence follows the addition, carbonate of ammonia has been formed from the urea; if there is a flocculent deposit, easily diffused by agitation, it is the natural mucus; if it is ropy and apparently viscid, and a drop of nitric acid dissolves it, it is composed of the phosphates. A white, brownish, or reddish deposit disappearing when the urine is heated, consists of the urates-a reddish one occurring in acid urine, consisting of particles like cayenne pepper is more important, being uric acid; it is soluble in alkalies, and, evaporated with nitric acid, presents the rich tint of purpurine. A deposit insoluble in acetic, but soluble in hydrochloric acid, and giving a white precipitate when neutralized by ammonia, is probably oxalate of lime. Cystine dissolves in ammonia with an aromatic odour. The microscope also detects the corpuscles of blood or pus, and the peculiar crystals of uric acid (spindles), the phosphates (prisms), and oxalate of lime (octahedra), in a ready way. Kreatine is also best detected by this instrument.

The industry of chemists has also been successfully applied to the analysis of calculi, but we trust that enough has been said to prove the close relation of medical science with the interesting discoveries of chemistry.

ΕΝΔΙΟ

CHAPTER IV.

Pathology-Apology for the different opinions which have been held with respect to the nature of diseases-Progress of our knowledge of medicine-The classification of diseases, their natural history, proximate causes, and indications of cure-Sthenic diseases, inflammations, epidemics, contagions, exanthemata, morbid poisons-Contagious and non-hereditary diseases.

WE are not now about to compose a treatise on the diseases of the human body; it may perhaps be considered presumption enough to attempt even a sketch of their natural history and arrangement, of as much as is known of their essential nature, and an epitome of the general indications of cure, enough to enable us to judge of the present acquirements and deficiencies of our art.

It has been written that medicine is a science of guessing, and that "it has been more professed than laboured, and more laboured than advanced," and that "this labour has been often in circles, and not in progression," yet we must maintain, that since Bacon's time, and particularly in the present century, these observations do less apply. In our own days how many improvements are taking place in medicine. Much light has been thrown on diseases of the heart and lungs by the stethoscope,* on head affections, on diseases of the kidneys and dropsies, on the morbid anatomy of diseased structures and tumours, and valuable additions have been made to the materia medica, as evinced in the discovery of iodine, chloroform, and the alkaloids.

In some respects, certainly, the most ancient of physicians was one of the greatest; since he was a true observer of his "nature," and her "powers." The necessary consequence of this doctrine appears to follow in that of crises; but other tenets which have been attributed to Hippocrates may not in reality belong to him, but appear to have been later additions of the dogmatical school, suppositions attended with a variable quantum of truth. Such doctrines of atoms, numbers, elements, humours, constriction, and relaxation, &c., have in all ages been the progeny of one form of the human mind applied to medicine, the methodic or systematic, the opposite to that empirical turn which would observe all facts but explain none. Another tendency still is to be seen in medical philosophy, to mount from matter and the body to spirit; to leave what we may understand, but which does not satisfy our curiosity, for what we wish to know, but which is above our reach; a principle which the historians of our art tell us influenced some of the eclectics in ancient medicine, as well as the vitalists amongst the moderns.†

We have previously mentioned the reason which authors

Hook appears to have seen the use which such a conductor of sound might be to the ear in the detection of disease.

Heberden, in his Commentaries, makes some observations on this subject.

assign for the decadence of the healing art in the first centuries of Christianity. Even Luther was not free from the doctrines of the divine infliction of diseases, and of their cure by supernatural aid.

In the ages of mediæval darkness, however, and from the mistaken researches of alchemy, originated a science destined to throw much light upon medicine-chemistry. The alchemists naturally conceived a scorn for the Galenists, though Van Helmont did not ignore the existence of a presiding vital force or archeus, which indeed was the case also with Paracelsus.* In our own country a species of medical fanaticism arose, of which Fludd, Digby, and Greatrix were curious examples.

The truths of natural philosophy, also, now began to be elucidated, and the doctrines of ebullition, combustion, fermentation, and inspissation, of atoms and pores, combined or not with the chemical doctrines of acids and alkalies, and countenanced by the discovery of the circulation, and the researches or writings of such men as Borelli, Pitcairn, Wintringham, Mead, and Hales, became prevalent.

But it was soon found that animal tissues and vessels are only partially ruled by the laws of natural philosophy, and reducible to its problems. The philosophic Sydenham was one of the first to oppose this school,† and the spiritual system again had a remarkable supporter in Stahl, with his vis medicatrix naturæ. Hoffman upheld similar doctrines, and the illustrious Boerhaave did not discard them, though, like many other true philosophers, he rather sought to lay hold of something more tangible in the mechanical and chemical doctrines. Van Swieten's work added lustre to

* Paracelsus commenced his professorship by burning the works of Galen. According to Cabanis he used to exclaim, “ Arrière moi, Grec, Latine, Arabe!"

The writings of Whytt and Willis had a tendency to direct the attention of the physician to the inherent and peculiar actions of animal bodies.

When attacked by his last illness Boerhaave wrote the following letter to a friend, in 1737, which we transcribe from Mr. Pettigrew: