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you will. This leads on to the Bohr atom, and its insufficiencies, which the matrix mechanics and wave mechanics have, as briefly described, so substantially reduced. The explanation of doublets and other features of the spectrum by the spinning electron and Pauli’s exclusion principle occupy the fifth chapter. The stage is then prepared for a discussion of the modern systems of statistics, with the difficult conception of a degenerate gas, which has proved so valuable for the theory of the conduction of electricity in metals, even if superconductivity still defies the theorists. This part of the book in particular reveals the master, the relation of the two new systems of statistics to one another and to the older Planck and Boltzmann statistics being exposed about as well as could possibly be done in so restricted a space. The final chapter contains a general discussion of the problem of chemical combination as seen by the modern physicist. There is ample evidence of the care which Dr. Sauter has devoted to his task of revision. In short, the book gives a beautifully balanced summary of some of the most fascinating developments of modern theoretical physics. E. N. DA C. ANDRADE.
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L i p o i d e uno! Ionen. By DR. A. DEGKWITZ. 15.5 x 22 cm.; xvi 323 pp. Dresden and Leipzig: Steinkopff, 1933. Price: bound, 29.20 M.; unbound, 28.0 M. This volume contains a somewhat general but very readable account of the properties of surface films and the action of the forces responsible for surface tension in effecting a molecular orientation as well as affecting chemical equilibria a t interphases. I n addition the more important properties of hydrophobic and hydrophilic colloidal systems are discussed. The partirular value of the book lies in the fact t h a t the author has been a t some pains to collect and sift the information available on the lipoids. It has, of course, long been a matter of dispute whether the physical functions of biological lipoids are merely to form a lipoid layer possessing all the properties entailed in the acceptance of the hypothesis of Overton and Meyer in respect to cell permeability and narcosis. I n many cases these layers must be reduced t o the dimensions of monolayers, and in those cases their specific and peculiar properties would appear to be of little value in accounting for the observed phenomena. No detailed examination of the effect of lipoids on proteins in the gel state appears to have been made, but the author has collected together the results of the experiments of Calabek, Meyer, and especially Bamberger on lecithin and cholesterol which appear highly significant. Of recent years the problem of swelling and contraction of amphoteric hydrophilic colloids, such as the proteins in the gel state, has attracted more attention and there is little doubt that the conditions of equilibrium envisaged by Procter and Loeb, namely those determined by the establishment of a Gibbs-Donnan equilibrium, is but part of the story. The restraint placed upon the system expanding on account of the differential osmotic pressure on this theory lies in the inherent extensibility of the network. The work of Astbury and Jordan Lloyd and others has shown that extensibility in solution is determined by the number and nature of the cross linkages, as well as by the balance between the hydrophobic and hydrophilic portions of the polypeptide chains. Increasing the number of cross linkages or decreasing the hydrophilic portions of the chain renders the extensibility in solution less. This is the variable not considered in the formal mathematical investigation. We know, thanks to the work of Kruyt and of Katz, that numerous substances whether ions or organic molecules are adsorbed by the proteins and affect the balance between the hydrophobic and hydrophilic portions of the molecule; thus tannic acid or amyl alcohol reduce the hydrophilic character, whilst thiourea and iodoacetic acid increase the number of hydrophilic groups. We may regard these substances in the terminol-
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ogy of the biologist as antagonistic to each other. It appears from an examination of the data presented by the author that lecithin behaves in a manner similar to thiourea, i.e., i t is a hydrophil donator, whilst cholesterol is a hydrophobe donator. A mixture of the two preserves an adjusted equilibrium. If this really be the case the way is paved for the interpretation of many phenomena such as the production of hemolysis by varied reagents.
ERICK. RIDEAL.
