tish physicians who are intrusted by their government with the treatment of this epidemical disease. These questions will enable me, perhaps, though at a great distance from the places where that dreadful evil rages, to make some useful proposals which may tend more quickly to moderate its violence, and finally to eradicate it. How happy should I think myself if I could in this manner not only contribute to save the eyes of a part of the British army, but even, perhaps, acquit a share of the great debt which Germany has contracted with England for the incalculable benefits of vaccination! The questions upon the exact answers of which depends the possibility of acquiring a precise knowledge of the epidemical ophthalmia which rages among British soldiers are the following: 1. How long is it since this epidemy has first made its appearance? 2. In what country was it first observed? 3. Has any peculiar cause been observed to which this disease may be attributed, either in those places where it first inade its appearance, or in those where it propagated itself afterwards? N. B. In answering this query, particular attention must be made to climate, to situation, to the changes of temperature, to the nature of the dust which is thrown in the eyes, to the water which is used daily for washing the eyes, to the articles of food, to the various dresses which are in contact with the head, for instance, neck-cloths, head ornaments, hats, caps, and the like, and still more particularly, to the manner of living of the inhabitants, and lastly, to the insects found in those places. 4. Does this epidemy remain fixed in one quarter? or does it spread gradually in the surrounding places? and if so, in which direction? 5. Is the propagation of the epidemy (if it really take place) a consequence of certain changes of the atmosphere, for instance, of damp weather? of violent winds? 6. Has the epidemical ophthalmia raged hitherto always with equal violence? or has it shewn sometimes evident remissions? 7. If those remissions have really been observed, in what weather have they occurred? and has the same state of the weather always been found to produce the same remissions? 8. Is it likely, or has it been ascertained that this ophthalmia is contagious? and what are the circumstances which facilitate and accelerate the contagion? 9. Has 9. Has there been hitherto any remedy for this disease, praised by the vulgar, as a preservative, or even acknowledged as such by physicians, with some degree of foundation? and what is it? 10. Is the course of this epidemical ophthalmia quick, or slow? 11. Does any difference in the rapidity of its course manifest itself sometimes in various individuals? 12. Has it been observed that this disease attacks principally a certain class of constitutions (organisms) or only particular habits, whilst it spares others? or does it attack every indi vidual who comes near enough to the sphere of its action, without difference of temperament, of age, of profession, and of rank? 13. As it is however impossible that every individual constitution could be attacked with equal force by this epidemical disease of the eyes, because every external effect must be relative, it is asked; which constitution suffer most violently, and in which it is most dangerous? 14. Is this ophthalmia always, or only in some subjects attended with a general disease of the whole frame? 15. Does that constitutional disease (if it exist) manifest itself before the ophthalmia, or only during its course? and in which period of it? 16. What is the intensity and the duration of that constitu tional disease? 17. What are its principal symptoms and periods? 18. Is it attended with considerable febrile symptoms? 19. Is the fever under the influence of which the constitu tional disease takes place, continued, remittent, or intermittent? 20. If a constitutional disease accompany this ophthalmia only in some individuals, what is in general their habit? 21. What is the succession of the morbid symptoms which are observed from the beginning to the end of the ophthalmia? N. B. The undersigned begs particularly the medical gentlemen to whom this question is proposed, to pay the greatest attention to the species, the duration, the intensity and the seat of the pain; to the various degrees of derangement of the functions of the eye, viz. to the state of the power of sight during the ophthalmia? to the various developments of light before the eye; to the aversion to light, &c. in one word, to all morbid phenomena in the eyes and surrounding parts, which collectively have some influence upon the sensations of the patient? 22. What is the succession of the morbid phenomena which takes place from the beginning to the end of this ophthalmia in the organic substance and form of the eye? N. B. To N. B. To render the answer to this question perfectly satis factory to the consulting oculist, it is necessary to describe with the utmost care which parts of the eye are attacked at the beginning of the ophthalmia, and to know whether the inflammatory action begins in the noble and most subtile parts of the eye, viz. in the retina, choroides, iris, and so forth, and proceeds from the internal to the external parts which surround the eye; or whether at first the external part of the eye, viz. the eye lids, the conjunctiva, the sclerotica, and the cornea are attacked by the ophthalmia; and whether consequently the di rection of the inflammatory action propagates itself gradually from outwards to the inside of the eye? 2o In answering this question, it will be particularly neces→ sary to examine, whether in the course of the ophthalmia a true suppuration occur, and in which part of the eye it takes place, or whether this ophthalmia follows the course of a merely adhesive inflammation; or lastly, whether visible extravasations of lymph or pus take place in the chambers of the eye, which gradually acquire an organisation, and produce unnatu ral adhesions of the different parts of the eye, for instance, of the uvea with the capsule of the crystalline lens, of the iris with the cornea, etc. 23. Is blindness the invariable consequence of this disease? or is there any example of patients undergoing it without loos ing the power of sight? 24. If this last sometimes happen, we ask, under which treatment is the eye most easily saved, and under which treatment is the sight most often, most easily, and most quickly lost? 25. Is the sight lost by a complete destruction of the globe of the eye (colliquatio, disorganisatio) or by the disorganisation of some parts of the eye? and which are those parts? 26. In the last case, viz. when the sight is lost by the destruction of individual parts of the eye, is the blind subject still eapable of some perception of light? and in what degree? 27. With those individuals which are happily cured, that is to say, those who still enjoy the faculty of seeing, does any defect in the appearance and the form of the eye remain? 28. Is the recovery usually slow, and with what symptoms is it attended? 29. Does the recovery require any particular treatment in order to avoid a relapse? On the Combination of Acids with Animal and Vegetable Substances. By M. THENARD. My researches upon the nitric, muriatic, and acetic ethers, and upon those obtained by treating alcohol with muriate of tin and oxy-muriatic acid,† have naturally led me to examine if it was possible to form them with the other acids. I have tried the action of these acids upon alcohol; and it was in making and varying these experiments I arrived at the sin gular result which I have had the honour to communicate to the Institutet; a discovery, that when the vegetable acids are pure, none of them, excepting the acetic, combine with alcohol with the loss of their acid properties: but on the contrary, when mixed with a mineral acid capable of condensing alcohol strongly, they all form with that body a combination in which their acid properties disappear, without the mineral acid taking any part in this combination. It is evident then, that whatever may be the mode of the combination of alcohol with a vegetable or mineral acid, the alcohol produces in these compounds the effect of a true saline base. Now the question is, whether the property of combining with acids, and also of neutralizing them, does not belong to all animal and vegetable substances. It is very possible that this is the case; for, since alcohol possesses this property, all these substances may also possess it. It was with a view to solve this question that the following experiments were made. I passed over 300 grammes of alcohol, oxy-muriatic acid gas made from a mixture of 1750 grammes of muriate of soda, of 450 grammes of black oxide of manganese, of 800 of concentrated sulphuric acid, and of 800 grammes of water. Almost all the acid and the principal part of the alcohol were mutually decomposed, and either generated or liberated a large quantity of water, of matter having an oily appearance, of muriatic acid, and a small quantity of carbonic acid, and a substance abounding in carbon; a result that agrees with what has already been published either by M. Berthollet in the Memoirs of the Acadsmy, or by myself in the first volume of the Memoires d'Arcueil. All these products have been separted with care, as I have noticed in those Memoirs ; one only has been subjected to a new examination, and that is the oily matter. (No. 140.) Vol. i. des Mémoires d'Arcueil. D d When When carefully purified by water and potash, it has the following properties, some of which have been already ob served in the memoirs I shall quote. It does not redden turnsole paper; it is white; it has a cool taste similar to that of mint, and a particular but not ethereated smell; it is heavier, yet less volatile, than water; it is very soluble in alcohol, but very slightly in water. It is volatilized by distillation with nitric acid, and partly decomposed; but the products of this decomposition vary according to the strength of the acid used. If the nitric acid be weak, much muriatic acid is produced, and little oxy-muriatic: if, or the contrary, the acid be concentrated, little muriatic acid is procured, but much oxy-muriatic acid of course this substance contains a very considerable quantity of muriatic acid. In the same manner, when it is passed through a red-hot iron tube a large quantity of acid is disengaged. Yet it is decomposed but very slowly by the strongest alkalis, even when dissolved with them in alcohol: hence the conclusion must be drawn, that the muriatic acid it contains is intimately combined with another substance. I have not yet succeeded in discovering what this substance is, because I have not been able to separate it from every thing else. Whatever that may be, it is certain that it is capable, like the alkalis, of neutralizing acids; and it may be presumed that it contains a large quan tity of carbon, sinec in the decomposition of alcohol and oxy-muriatic acid, much water and very little carbonic acid are produced. But of all the vegetable substances, I am acquainted with none that possess the property of uniting themselves to acids, in a more eminent degree than some of the essential oils; perhaps even all of them enjoy this property. That of turpentine absorbs nearly one-third its weight of muriatic acid gas, and becomes converted, with the emission of much heat, into am almost entire crystalline substance. Kind some years since discovered it; its nature was afterwards studied by Tromsdorff and some French philosophers, and last of all by Gehlen. All these chemists, except Gehlen, have considered it as an artificial camphor, because it had the smell, volatility, lustre, whiteness, and many other properties of natural camphor; and comparing the action of muriatic acid on oil of turpentine, with that of sulphuric acid on vegetable substances, they have conceived that the transformation of this oil into camphor is solely to be attributed to the loss of oxygen, and hydrogen being abstracted in sufficient quantity by the muriatic acid to form water, and to a slight separation of carbon at the same time; in fact, that the artificial camphor with |