DOCTOR YOUMAN’S International Scientific Series promises to be an admirable collection of popular treatises. Ur. Edward Smith, well known to physiologists for his many careful researches in vital statistics, has given us a volume here on Foods, not unworthy to rank with its forerunners, and promises to follow it up by another on Dietaries, The present work courts comparison with the Lectures of Professor Letheby on the same subject, published a year or two ago. Doth are full of information of a sort useful to everybody ; but while Lethcby’s book enters a little more fully into the physiology of digestion, and has a chapter upon dietaries, Dr. Smith’s work is ampler and more practical in its account of particular articles of food, is more simply and clearly arranged, and, when its companion volume is added, will no doubt supplant the earlier and (then) the smaller work. Each kind of food is treated by itself; and Its mode of cultivation, the common impurities and adulterations to which it is liable, and the different manners in which it may be prepared, with their respective merits, are successively described. This makes quite a fascinating sort of hotch-potch to take up and read for half an hour ; and as it is hard either to criticise otto give an account of the “general drift” of a book composed almost wholly of separate facts, we are reduced to noticing a few points at random. Liebig’s extract of meat, for instance, which is so largely consumed, and still believed by the public to be nutritious, is reaffirmed by Dr. Smith to belong solely to the class of stimulant condiments. “ There is but little left in the extract to nourish the body, and the elements which it really possesses are salts, which may be obtained otherwise at an infinitely smaller cost, and the flavor of meat which disguises the real poverty of the substance.It should be classed with such nervous stimulants as tea and coffee, which supply little or no nutriment, yet modify assimilation and nutrition. Used alone for beef tea, it is a delusion.”

Under the head of horse-flesh, he says that, considering that the poorer classes in England “strongly object to eating anything which is regarded as of inferior quality or rejected by their richer fellow-citizens, it is really useless to bring the subject before public attention in this country,” — a mode of dealing with the matter which may be practical; but in a book designed to enlighten public opinion, one looks for a touch more of the enthusiasm of reform. In speaking of pork, too, he might well have devoted a few lines to refuting the vague prejudice against it -which is so common in this country, but for which few can give any reason beyond the fact that it contains trichinae and “measles,” and took longer to digest than other meats in the fistulous stomach of the celebrated St. Martin. This latter undesirable quality, Dr. Smith says, is due to the hardness of the muscular fibres, which need more mastication than those of other meats.

Under the heading of wheaten flour, he compares the value of meal made from tire entire grain with that from which the outer particles have been sifted, and justifies popular prejudice, which insists on sticking to its loaf of fine bolted flour, in spite of the warnings of that numerous school which believes that salvation depends on “ Graham ” flour. Both he and Professor Letheby give the palm for composition and digestibility to “’seconds” flour, which is of the degree only once removed from the finest. The coarser qualities, which contain more of the hull, are, it is true, richer in gluten and in salts, but are, as Voit of Munich has recently confirmed, less completely digested. The indigestible part of the bran excites the bowels so much that a part of what otherwise would be absorbed is carried off with it. So Graham bread makes a less instead of more economical food for the poor. For many, to whom the superiority in economy is unimportant, it is, however, no doubt the better article. And we may say, in passing, that few people know by experience whether Graham flour suits them well or ill, for few have tasted it finely ground and made of the best wheat. The stuff usually sold by that name is made from wheat unfit to make white flour, and often has had extra bran added to it. The best Graham flour certainly has not that inferiority of flavor which our author ascribes to it ; and there are some observations on the improvement of children’s teeth under its use which may make one suspect that its whole alimentary history is not disposed of when we have found that most of its nitrogen is wasted in the bowels.

After all, not physiological analysis, but the rough verdict of long practical use, where one could get true comparative data by it, would be perhaps still our safest guide, if we must needs have one exclusive guide in dietetics. We are led to this remark by Dr. Smith’s articles on tea and alcohol, in which his conclusions are in large part inferences from the direct physiological effects of the fluids when taken in. Thus, because tea largely increases the amount,of carbonic acid exhaled, he considers it favorable to “vital action,’’whilst his verdict is as unfavorable to gin, brandy, and wln.-key, because they diminish the same excretion. And because the alcohols do not exert*their maximum effects in a precise! v corresponding way on the different functions which arc influenced by them, he savs they “ disturb ” the vital harmony, and hence are bad. But who is not aware how small a portion of the facts these are, and how great is the set of secondary and tertiary changes set in motion by these primary ones, of which we know nothing accurately,* but which, in the question of the chronic advantages or disadvantages of the beverage, become the most important elements ? Dr. Richardson, in an article against alcohol of which our author quotes a part, makes a great point of the waste of energy it produces by accelerating the heartbeats ; and goes into a sensational calculation of the amount of work in foot-pounds which one may thus throw away. But is not exercise good ? and do we not throw away in exercise an immense amount of work in quickened heart-beats ? It is vei v likely that Dr. Smith’s thesis against alcohol is true in the main, though his indiscriminate laudation of tea is undoubtedly false. But in either case, most of the reasoning from physiological analysis of the effects is crude, shallow, and really unworthy of the physiology of to-day.

A good instance to enforce our own point of view is to be found in the chapter on milk, in which observations are quoted to show that children fed on “condensed milk” though they grow very fat and look uncommonly healthy, arc yet slow in learning to walk, and show no power to resist disease. Now, condensed milk only differs from ordinary milk by the addition of sugar. We know nothing of the effects of sugar which should make us expect beforehand such a result from the use of tire milk. Indeed, on Dr. Smith’s principles, it ought to be a most beneficial addition, for its power to increase the respiration is extraordinarily high.

But the vice we speak of is characteristic, not so much of the present author as of the mode of treating such questions which still prevails nearly everywhere, and which is certainly but a half-way house towards the true one.

— It is perhaps not too extravagant praise of Helmholtz, now Professor of Physics in Berlin, to say that he is the greatest scientific genius now living. He has touched no subject without breaking new ground in it. The whole science of acoustics'may be said to have been renovated by him. His great work on physiological optics will always be a model of tlie profound and thorough way in which one man may exhaust a subject. Though not professedly entering into psychology proper, the elaborate study he has made therein of our visual perceptions forms perhaps the most really important contribution to psychological science of our generation. One hardly knows which to admire most in this work, — the mathematical originality, tire ingenuity of mechanical contrivance and experiment, the genius for patient observation and subtile interpretation, or the power of large constructive thought which gives unity to the whole. He is, perhaps, most popularly known by his invention of the ophthalmoscope, that instrument for seeing into the interior of the eye, which has transformed oculistie medicine. He was the first to study muscular contraction by means of recording instruments, and the first to measure the velocity of the nervous current. When we add that his other scattered investigations in physiology, electricity, and mathematics would fill a long list, and that he is one of the four independent discoverers of the principle of conservation of energy, we need say nothing more to justify our opinion that this translation of his popular essays is an important addition to English scientific literature. Two of the essays are rtsumes of his researches on sound and vision, two on the correlation of forties, two on the general relations of physical science, one on glaciers, and one — a very interesting one — on Goethe as a scientific investigator.

We have not space for any detailed account of the separate papers. We will merely note, in passing, how the author’s study of the: eye, made with no reference to the theory of evolution, corroborates that theory, and discredits the old Hridgewater treatise doctrine of the eye being the most perfect of optical contrivances. “It is not too much to say,” he writes, “ that if an optician wanted to sell me an instrument which had all these defects, I should think myself justified in blaming his carelessness in the strongest terms, and giving him back his instrument.” He then explains that “ as our intelligence uses the eye and interprets its faulty data, it is quite sufficient to its function.” A sensible man will not cut firewood with a “ razor,” and a more perfect eye would be a superfluity.

It is interesting in this day of philosophic disintegration to know the general philosophic attitude of such a man as Helmholtz. He is very' sober and reserved in his utterances. But in his paper on Goethe there is a passage which we may quote. After showing how Goethe, the poet, sought in nature the direct and transparent sensible expression of the spiritual, and so went astray, he goes on : “ The natural philosopher, on the other hand, tries to discover the levers, the cords, the pulleys which work behind the scenes, and shift them. Of course, the sight of the machinery spoils the “ beautiful show,” and therefore the poet would gladly talk it out of existence, and, ignoring cords and pulleys as the chimeras of a pedant’s brain, he would have us believe that the scenes shift themselves or are governed by the idea of the drama. .... But we cannot triumph over the machinery of matter by ignoring it; we can triumph over it only by subordinating it to the aims of our moral intelligence. We must familiarize ourselves with its levers and pulleys, fatal though it be to poetic contemplation, in order to govern them after our own will ; «md therein lies the complete justification of physical investigation, and its va$t importance to the advance of human civilization.”

  1. Foods. BY EDWARD SMITH, M. D. New York : D. Appleton & Co. 1S73.
  2. Popular Lectures on Scientific Subjects. By H. HKI.MHOTTZ. Translated and edited by E. ATKINSON. New York ; D. Appleton & Co. 1873.