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Introduction IN"the latter half of the nineteenth century there developed a great wave of interest in cytology and histology. The experimental basis of this wave was the use of synthetic dyes for the staining of fixed sections. One of the main driving forces behind it was the desire to obtain information about the organisation of protoplasm, on both the physiological and chemical levels. On the physiological level many observations of great value were made; but on the chemical level very little of any value was obtained. The criticism of such shrewd observers as W. B. Hardy1 and A. Fischer2 made it plain that, with the usual techniques of fixation and staining with synthetic dyes, the results obtained were as much a function of the nature of the fixative, the physical characteristics of the fixed material, and of the technique of staining, as of the chemical and physical nature of the original protoplasm. Hence by the early years of this century the wave of interest in cytochemistry had lost much of its momentum, and was succeeded by a wave of interest in the experimental study of the living cell.

STUDIES by G. R. Cameron and his colleagues had O shown by 1942 that in systemic lewisite poisoning a condition prevails in the first few days which in some particulars resembles traumatic shock, being marked by haemo concentration. It was found that administration of plasma, or of other fluids, was of no avail in reducing the mortality caused by a given dose of lewisite. It was therefore decided that the first step in the treatment of lewisite poisoning must be the inactivation of at least that part of the arsenical causing shock.

IN a number of cytochemical papers1,2 it has been claimed that α-hydroxyketones, such as deoxycorticosterone, give a purple colour with reduced fuchsin in Feulgen‘s ‘plasmal' reaction. In this reaction the material under test is treated with cold saturated aqueous mercuric chloride solution, then with reduced fuchsin. According to Dempsey et al.3, aqueous mercuric chloride oxidizes the hydroxy-ketone to an aldehyde, which then reacts with reduced fuchsin.

IT has long been known that when a fertilized egg is flattened between two plates it may cease to divide. Zeuthen1 has shown recently that although cell division is inhibited, nuclear division may continue, so that many nuclei may be present in a single flattened cell. I obtained essentially similar results during the summer of 1951, at Roscoff. It Was found that, if the egg was not too greatly compressed, it would eventually divide and, once division set in, cleavage of the cytoplasm would continue until the normal ratio of one nucleus to one cell was re-established.

USING the technique of nuclear transfer1, it has been shown that many of the cellular properties of the large, uninucleate amœbae, Amoeba proteus and A. discoides, are influenced by self-replicating cytoplasmic hereditary determinants. The characters determined in this way are those which depend on the way in which macromolecules, the specificity of which has been determined by nuclear genes, are organized into functional units2.

Histochemistry Theoretical and Applied. By Dr. A. G. Everson Pearse. Pp. viii + 530 + 35 plates. (London: J. and A. Churchill, Ltd., 1953.) 60s. net.

The Physiology of Insect Metamorphosis By Prof. V. B. Wigglesworth. (Cambridge Monographs in Experimental Biology—No. 1.) Pp. viii + 152 + 4 plates.(Cambridge: At the University Press, 1954.) 12s. 6d. net. The Genetics of Paramecium aurelia By G. H. Beale. (Cambridge Monographs in Experimental Biology—No. 2.) Pp. xi + 179. (Cambridge: At the University Press, 1954.) 12s. 6d. net.

DR. JUST has written an interesting account of his personal views on a group of subjects including fertilization, cell division, and the function of chromosomes. The first part of the book, dealing mainly with the structures, functions, and movements of the ectoplasm (the outer layers of the protoplasm) of marine eggs, contains a large amount of material on which there, is fairly general agreement. The following chapter, on water, deals with the movements of water in eggs, and between eggs and their environment. It is stated that when eggs are placed in hypertonic saline, water leaves the egg in discrete droplets, which apparently have to pass through comparatively narrow channels in penetrating the ectoplasm. This extremely interesting observation, if confirmed, would invalidate the majority of the work which has been done on the permeability of marine eggs, in which it is assumed that water leaves the egg by simple diffusion. In the same chapter, Dr. Just betrays some doubt as to the existence of a relatively impermeable membrane at the surface of the cytoplasm. There is to-day no ambiguity on this point; the impedance studies of Cole (J. Cell. Comp. Physiol., 1, 1; 1932; J. Gen. Physiol., 18, 877; 1935) have shown that such typical eggs as those of Arbacia and Hipponoe have a membrane which is impermeable to ions, while Chambers (Biol. Bull., 69, 331; 1935) has shown by microdissection that this membrane is liquid and fatty in character. The Biology of the Cell Surface By Ernest Everett Just. Pp. xi + 392. (London: The Technical Press, Ltd., 1939.) 26s. net.

IN the Gomori–Takamatsu technique for localizing alkaline phosphatase, tissue sections are incubated in a solution containing a phosphate ester and calcium ions. The phosphate ions liberated as a result of enzyme activity are precipitated in the section as calcium phosphate, which is made visible by converting it to cobalt sulphide. The cobalt sulphide is dark brown and gives only a rough indication of the degree of enzyme activity. A quantitative method1 has recently been developed for measuring the mass of substances (other than water; that is, dry mass) in cells. It has been shown that the dry mass can be determined from measurements of optical path difference which can be made with an interferometer microscope. This note describes measurements made with this technique of the amounts of calcium phosphate deposited as a result of phosphatase activity. We have found that the interferometer-microscope method can be used to study the magnitude of possible artefacts due to diffusion of enzyme and diffusion of the calcium phosphate. We have also found that interferometry provides a most promising approach to the quantitative determination of enzyme activity at sites in cells.

THE recent work of Butenandt, Marrian, and others on the oestrus-producing hormone, summarised in the Chemical Society's discussion on March 161, has consolidated our knowledge of the chemistry of these substances and shown that they are probably closely related to the sterols. It appears opportune to adopt a uniform chemical nomenclature for the derivatives of oestrin, which harmonises with that used for the sterols, and we suggest the following.

Jacoby and Martin1 have recently pointed out that diffusion of phosphatase may occur during the process of incubation which forms part of the technique of Gomori and Takamatsu for the cytological demonstration of alkaline phosphatase. I can confirm that artefacts may arise in this way. But there is no difficulty in deciding to what extent the results obtained by this method are valid, provided the technique is supplemented by some additional techniques published in 19462.

THE basic difficulty in devising a method for selectively increasing the density of protein in a tissue section, in order to increase its contrast under the electron microscope, is to choose some atom or group of atoms unique to the protein, and which may be replaced or substituted by some heavier atom or group. The amide group occurs in all proteins as the peptide link, while it is absent in all other macro-molecular cell constituents. N-chlorination(·NH·CO·→·NCl·CO·) is a well-known reaction with simple amides, and it therefore seemed that chlorination might offer a simple means of increasing the density of the protein. Although chlorination of other cell constituents (and other structures in the protein) would undoubtedly also occur, it was considered that the background increase in density produced in this way would be small compared with the increase in density of the protein, for theoretically 1 gm. atom of chlorine can react with each 100–150 gm. of protein, depending upon its amino-acid composition. Vandevelde1 has shown that many proteins, both fibrous and globular, react with chlorine to give materials which contain about 15 per cent chlorine, a content which corresponds to substitution at most of the peptide links. Most of the chlorine is lost from the modified protein by treatment with water, giving hydrochloric acid, which probably arises by hydrolysis of the N—Cl bond followed by oxidation of the protein by the hypochlorous acid which is formed. Exposure to chlorine gas, followed by spraying with iodine and starch solutions, has been used as a delicate test for amino-acid, peptide and protein spots on paper chromatograms2.

WHEN the tissues of Craniata are treated by the technique of Takamatsu1 and of Gomorri2, alkaline phosphatase is found to be present in the cell nuclei. Willmer3 has observed that in mitosis in tissue cultures the nuclear phosphatase is concentrated on the chromosomes. One of us (J. F. D.), in collaboration with Dr. H. B. Fell, has found phosphatase on the chromosomes in tissue culture mitoses, and in the mitoses of healing wounds. That the enzyme is indeed in the cell nuclei may be shown in many ways4; for example, on heating dry rat kidney sections phosphatase not in the nuclei is destroyed more rapidly than is nuclear phosphatase, so that, by careful timing, sections may be obtained in which only the nuclei contain active phosphatase.