Scripture, E. W.

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SCIENCE. [N. S. VOL. VI. NO.134. must result in many.invalids being deprived of a luscious and digestible food, and last, but not least, help to belittle science by reasoning which the common sense of centuries shows to be absurd. Contrast all this with the calm attitude of the scientific British Medical Journal, which contents itself, according to the cluotation from it, with calling for scientific investigation of the reason for some beds being polluted.* I t  seems quite likely that isolated oyster beds might be con- taminated with bacilli, but the natural history of the oyster shows that he could not exist under such conditions, and that the bed would die out. In fact, the danger will apparently regulate itself. I hope that these remarks will draw the at- tentibn of practical biologists, competent to set the question a t  rest ; at  the same time they will serve to show the great need of a t  least an ele- mentary knowledge of science among our doc- tors before they presume to settle questions of the food supply of mankind; and they will serve to show the great lack of that knowledge among the rank and file of practitioners, who, a t  any rate, 'out west,' appear rather to glory in it. GEORGECHAS. BUCHANAN. CEREBRAL LIGHT. INdarkness or with closed eyes we can al- ways see irregular forms of light in our visual field. These forms are of various kinds, series of waves, successive rings that spread and break, etc. In  addition to these definite figures there is always more or less definite irregular illumi- nation over the whole field. These phenomena are generally called the ' retinal light ' or the 'Eigenlicht of the retina.' They are usually supposed to arise from chemical changes going on in the retina. I wish to record some obser- vations that apparently prove them to be cere- bral and not retinal processes. 1. With closed eyes there is only one illumi- nated field, not two, as there should be from the two retinas if the light were retinal. Two retinal figures might appear as one under the * Cf. The investigationsby Professor Conn, of Wes- leyan University, and of Professor Herdman, of Liv-erpool College. conditions: (a) Of suppression of one field, which is not the case here, because i t  is impos- sible to keep one field suppressed for many minutes, whereas I have watched the retinal figures in uninterrupted continuance for a long time ; (b )  of perfect identity of form, which is hardly a possible supposition in the case of these irregular, volatile, chemical phenomena ; (c) of sufficiently similar construction for union by stereoscopic vision, which also is not the case, as there is no relief effect in the picture. 2. The figures do not change in position when the eye is moved. They are localized in front and remain in the same place, even if the eyes are directed to one side. I find, however, that if the eyes are turned to a new position and kept there, the central figure (a spreading violet circle with a phosphorescent rim) will soon afterwards follow the movement ; there ir thus a tendency for this figure to occupy the spot of sharpest vision. 3. The figures do not change in location when the eyes are displaced. When the e y y  are looking a t  some definite object, e. g., this page, a pressure of the finger on one of them will cause the page apparently to move. This is true whether the other eye is open or closed. Like-wise, if an after-image is obtained, it will move upon pressure of the eyeball. The pressure dis- places the eyeball and changes the projection of the retinal picture. This displacement does not occur with 'retinal light.' I have repeatedly observed these figures and have manipulated the eyeballs ; I have found that they are not in the slightest degree affected by the manipulations. In order to avoid all possibility of errors of ob- servation, I have made the experiments in a series alternately with eyes open and eyes closed. With the eyes open I observed a dimly illuminated window; with them closed I saw the ' retinal ' figures. The former always fol- lowed the displacements, the latter never. These observations are, I believe, sufficient to establish the proposition (which I have not seen elsewhere) that the phenomena of vision usually known as ' retinal light ' and ' retinal figures ' are not originated in the retina, but in the brain. They should therefore be termed ' cere-bral light ' and ' cerebral figures.' The following hypothesis seems also justified : SCIENCE The cerebral light is located in those higher cen- ters of the brain which are connected with vis- ual memories and imaginations. While watch- ing the cerebral figures I find that my visual memories or phantastic figures appear in the midst of the cerebral light and frequently can- not be distinguished from them. The close con- nection of these cerebral figures with the con- tents of dreams has been repeatedly noticed by Johannes Bliiller and a series of later observers. There is also the possibility that the hallucina- tory visions produced by hashish, mescal and other drugs may be simply modifications of this cerebral light. E. W. SCRIPTURE. YALE UNIVERSITY, May 21, 1897. SCIENTIFIC LITERA TURE. Grundriss der Ent~wickelungsgeschichte des Menschen und der Siiugefhiere von DR. MED. OSCARSCHULTZE. Bearbeitet unter Zugrund- elegung der 2.  Auflage des Gsundrisses der Entwickelungsgeschichte von A. Kolliker. Leipzig, Engelmann. 1897. 8vo. Pp. vii + 468. Kolliker's well known manual has been so thoroughly reworked by Professor Schultze that it is essentially a new work. In Kolliker's volume the embryology of the chick furnished many of the descriptions and illustrations. Schultze has omitted the chick altogether, con- fining himself strictly to mammalian develop- ment, and has added a comprehensive though very condensed account of the fa ta l  mem-branes and placenta in the chief groups of mammals. Many new and admirable figures have been added, of which a considerable majority are original and taken from the author's own preparations. I t  is exceedingly difficult to characterize Professor Schultzels text-book fairly, for it combines superior merits with conspicuous and singular defects. I t  is utterly inadequate as a presentation of contemporary embryology, for i t  systematically neglects the morphological, phylogenetic and mechanical aspects of embry- ology, and consequently reads almost like an old-fashioned descriptive anatomy. An embry- ological writer might be excused for avoiding phylogenetic and mechanical themes, but the neglect of morphological considerations makes full success in writing a text-book an impossi- bility. To illustrate these criticisms it suffices to examine the account of the nervous system ; in the development of this the history of the neuro blasts and of the division of the medullary tube into dorsal and ventral zones are the fundamental facts morphologically, but our author barely describes the neuroblasts, does not figure them at all, and makes no allusion to the two zones, which should form the basis of the whole account, for without understanding these zones no student can master even the rudiments of our present knowledge of the brain and spinal cord. Again, the epidermis is equally maltreated, for the history of the epitrichium is incorrect, and no mention what- ever is made of the fact that the nails are modi- fications of the stratum lucidum. Erroneous are also the accounts of the development of the glands in the stomach, which do not develop in the same way as those of the intestine ; mis-leading is the history given of the supra-renals, for the so-called medulla of the organ in the human species is not derived from the sympa- thetic Anlage. There are mistakes in the illus- trations : in Figs. 194 and 195 the 'Zwischen-hirn ' (Diencephalon) is correctly designated, but in Figs. 217 and 263 the same division of the brain is called 'Mittelhirn ' (Mesence-phalon) ; in Fig. 327 the left side of the heart is called ' rechte  Kammer ' and the right side ' linke Kammer,' while the great vein is labeled Sympathicus !' Of the index complaint must be made : one searches it in vain for Hirnblasen, Nerven, Thyroidea and other headings. In spite of these criticisms, which indicate that the usefulness of the book is severely limited, the manual remains one of many merits and of great value. The author is fe- licitous in his combination of brevity and clear- ness, and in avoiding cumbrous accumulations of details. The faulty illustrations are excep- tions; very good ones indeed are the rule, good both in selection and execution. In prinMng them the publishers have sustained their high reputation in this regard. The author has studied a t  first hand, and is thereby enabled to make his descriptions fresh, vivid and interest- ing, and if he had included in his poist of view 

Cerebral Light

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Cerebral Light

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