normal alkaline cultures are positive to alkalies (which cause liquefaction), and negative to acids (which cause coagulation). The present reviewer emphasized in his first paper on the reactions of Paramecium (Journ. of Physiol., vol. 21, p. 268, p. 317) a result that is precisely the opposite of this. Paramecia from alkaline cultures were found to be negative to alkalies and positive to weak acids. From the results of literally thousands of experiments, many made since GREELEY'S work appeared, I am compelled to reaffirm this result. Paramecia then are positive to acids, which, as GREELEY finds, are coagulative in their effects.

6. Paramecia in acid cultures are, according to GREELEY himself, positive to acids. Yet acids cause coagulation under all circumstances, again according to GREELEY.

7. To strong alkalies Paramecia are under all circumstances negative. Yet strong alkalies cause liquefaction. This shows that liquefaction is not the ultimate determining feature in the positive reaction.

8. To all substances mentioned on page 11 of GREELEY'S paper as causing liquefaction, Paramecia are negative, while to a number of those listed as causing coagulation they are positive.

GREELEY'S generalization is therefore in direct conflict with many of the best known facts in the behavior of these organisms. It is no doubt true that as a rule Paramecia avoid strongly coagulating agents, for they avoid most injurious agents, and coagulation of the protoplasm is one of the commonest injuries produced by external agents. But they equally avoid agents that cause liquefaction beyond a certain stage, and they react in the same way to many conditions that are not known to cause either liquefaction or coagulation.

The only basis on which GREELEY'S theory might give a plausible generalization as applied to electrotaxis would be the following. It might be said that liquefaction, produced at the cathodic end of the organism, is connected in some way with the reversal of the cathodic cilia. But under other circumstances the cilia are reversed when there is no indication of liquefaction, as in swimming backward in a strong acid which causes coagulation.

The paper of BIRUKOFF (7) is a defence of the theory that the movement of infusoria to cathode or anode is due to a passive transportation by the cataphoric action of the current. Since Paramecia in ordinary water go to the cathode, while in salt solution they go (according to BIRUKOFF) to the anode, the amount of electromotive force developed on the bodies of the animals during the passage of the cur

rent should be different in the two cases. The experimental portion of the paper consists in a demonstration, by means of fitting apparatus that this is actually the case.

This result shows only that there is nothing in the conditions to make such movement as BIRUKOFF assumes a priori impossible. It of course by no means shows that electrotaxis actually takes place in the way BIRUKOFF supposes. BIRUKOFF's theory for these conditions is really completely disproved by the fact, set forth by PÜTTER and others, that after the Paramecia have been for a short time in the salt water, so as to become accustomed to it, they no longer go to the anode, but as usual to the cathode. BIRUKOFF Of course recognizes that this if true is fatal to his view. He attempts to meet it by assuming that PUTTER'S observations were due to preposterously crude experimental errors, and that the facts are not really as PÜTTER states. But the facts have been established beyond doubt, not only by the observations of PUTTER, but by the careful work of STATKEWITSCH above set forth. The present writer can testify from his own observations to the accuracy of their accounts.

It seems incredible that anyone should yet, after all the thorough work that has been done on the movements of the cilia, hold that the movement to cathode or anode is a passive one, due to the cataphoric action of the current. This possibility is of course the first one to occur to the observer, and it is the first one to be dismissed after the facts are carefully observed. Before the current is passed through them, the infusoria are moving about in all directions. Now the current is closed, and all continue to move at approximately the same rate as before, but they all now swim towards the cathode. There is then not the faintest shred of evidence that the movement is due to cataphoresis. The movement existed before the cataphoresis came into effect; the only essential difference between the later motion and the first one (with one exception to be mentioned) is that the movement is now directed toward the cathode. The observed movements of the cilia, which are demonstrated by the currents produced to be powerful, must cause the animals to move forward, just as when no electric current was acting. There is no reason whatsoever for calling in the cataphoric action to transport the animals; there is nothing for it to do.

The one difference in the movement of the cilia is the fact that some of the cathodic cilia show a reversed stroke. Neither BIRUKOFF nor anyone else has attempted to show how this can be a direct effect of cataphoric action. The observed movements of the cilia account

fully for the movements to cathode or anode. The turning into orientation is likewise fully accounted for by the opposed movements of cathodic and anodic cilia. BIRUKOFF seems inclined to doubt the observations of LUDLOFF on this point, but these observations have been confirmed by many investigators, and there is really not the slightest difficulty in repeating them and perceiving their accuracy. What is not accounted for is of course the observed effects on the cilia, particularly the cathodic reversal. It is here that further investigations should take hold.

Though BIRUKOFF starts with the thesis that the movement is due to cataphoric action, one finds that he admits in the course of his somewhat rambling paper various other factors. All difficulties with his theory are solved by bringing in the conveniently vague "general irritability" of the organism as an additional factor. He even admits, toward the end, after many pages of argument against it, that the "polar stimulation" of VERWORN may have something to do with the One wonders finally whether BIRUKOFF himself really believes that the movement is due to cataphoric action.

matter.

It is of course possible that cataphoresis acts in some way as a stimulus to produce the observed movements of the cilia, just as it is possible that the neutralization of electric charges in the protoplasm may be in some way connected with the movements. But neither GREELEY nor BIRUKOFF have even so much as attempted to show how

Little real advance in our understanding of the reaction to electricity is to be expected from writers who ignore the fundamental phenomenon -the peculiar action of the current on the cilia.

H. S. JENNINGS.

LITERARY NOTICES.

Nagel, W. (Herausgeber). Handbuch der Physiologie des Menchen.

Dritter

Band (Physiologie der Sinne,, Erste Hälfte, XII+ 282, 1904. Braunschweig, Vieweg und Sohn.

This first installment of NAGEL'S "Handbuch" forms a little more than a third of the volume devoted to sense-physiology, and, except for two short introductory articles on the doctrine of specific energies (NAGEL, Berlin, pp. 1-15), and the psychology of the senses (v. KRIES, Freiburg, pp. 16-29), it is confined to physiological optics. SCHENCK (Marburg) presents dioptrics and the accommodation of the eye (pp. 30-90); NAGEL, the effects of light on the retina (pp. 1-108); and v. KRIES, visual sensation (pp. 109-282). Visual perception, and the nutrition and the protective organs of the eye are left for the second half of the volume and will not, therefore, be considered in the present review.

Both introductory articles deal with certain concepts common to all the senses. To place JOHANNES MÜLLER'S doctrine of specific energies beyond dispute, it would be necessary to show that different stimuli, acting on the same nerve, produce the same sensation. NAgel mentions that the only really clear confirmation of this kind is the taste sensations that result when the chorda in the cavum tympani is mechanically, electrically or chemically stimulated He concludes that while the doctrine, with certain reservations in the case of the lower senses, is doubtless in general valid, the efforts, dating from HELMHOLTZ, to show the existence of separate nerves with correspondent specific energies within the individual sense-organs are not successful; for the differences in sensation may just as well be due to the differences in the outward stimuli as to the specific energies of the ner ve fibers themselves.

V. KRIES's introductory discussion of the psychology of the senses is important chiefly as a general estimate of the value of psychological analysis for sense-physiology, a question which receives repeatedly more specific attention in his longer article on visual sensation. Of special interest is his view of the theoretical possibility of measuring sensations (FECHNER'S Psychophysic Law), and his treatment of the theory of specific comparisons, i.e. comparisons between sensations

that are not wholly alike, "but between which, in addition to a definite difference, a certain similarity exists" (p. 22).

The first two articles on vision proper, dioptrics (SCHENCK), and the influence of light on the Retina (NAGEL), bring up to date what is known about these more objective phenomena of physiological optics. A colored plate, in the latter, shows well the movements of the cones and the pigment of the retina.

Nearly two thirds of the present half-volume are occupied by v. KRIES'S suggestive and subtle contribution to visual sensation. The essay is subdivided as follows: laws of color-mixture, visual sensations and their psychological ordering, dichromatic color systems, adaptation of the visual organ, eccentric vision, after-images, local and color changes in the disposition (Umstimmung) of the visual organ, temporal relations of the effects of light, induced light and color sensations, limits of perception and discrimination, modifications in the color sense brought about experimentally or by disease, effects of inadequate stimuli, review of the facts and the results considered with reference to the theoretical conception of the visual organ.

It is possible to consider here only two points, -the author's general methodological views, and his estimate of present achievements in fact and theory.

As to the first point, it is evident that at almost every step the author feels the necessity of separating sharply the psychological method, "for which the mutual relations of the sensations are of chief importance, their dependence on stimuli, however, of lesser significance" (p. 109), from the physiological method, for which the paramount problem is the relation of the reactions of the visual apparatus, as indicated by the sensations, to its adequate stimuli, and of the resulting facts to the objectively demonstrable properties of the visual organs. An instance of the latter method is, of course, the attempt to refer "day-vision" to the cones, and "twilight vision" to the rods. V. KRIES admits the possibility of a psychological analysis of the sensations, but, since he questions certain current psychological inferences drawn from such analysis, and condemns attempts to reach, through a psychological ordering of the sensations, conclusions concerning the physiological processes involved, he is skeptical as to the value of the analysis. It is possible, for instance, with AUBERT and HERING, to pick out red, yellow, green and blue as four colors having no mutual resemblances in quality, but "an unbiassed person would hardly select blue in complying with a request to designate a sensation which is the contrary of yellow" (p. 135). It is doubtful, namely, whether the