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Volume 16 - October 1926

Contents

Page 3 of 3

Front matter

  • AGS volume 16 issue 2 Front matter

  • Published online by Cambridge University Press:
    27 March 2009, pp. f1-f5
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Research Article

  • “Apparent ropiness” (thread formation) in milk due to surface influence

  • A. T. R Mattick
  • Published online by Cambridge University Press:
    27 March 2009, pp. 459-465

  • A physical form of “ropiness” in milk has been described and shown to be due to the formation of thin films of casein and (or) lactalbumin at the milk-air interface.

    The “ropes” are a form of the “mechanical surface aggregates” of Ramsden and may occur on appropriate surfaces, such as ordinary farm coolers whenever the rate of flow, the temperature and the acidity conditions are favourable.

    A modification of Ramsden’s method demonstrating the formation of mechanical surface aggregates, in an hitherto unobserved form, has been described, viz. horizontal glass tubes in parallel which are especially suitable for opaque fluids.

    The condition appears to be identical with that described by Aekma and Brouwer(2) who showed the occurrence of corpuscles in milk after violent agitation. These corpuscles probably consist of thin films of solid protein which as in the cases described by the author have formed at the interfaces of air bubbles and milk.

    The phenomenon has been shown to be of importance in handling dilutions of milk in the course of bacterial enumeration.

  • The mechanical analysis of soils: A report on the present position, and recommendations for a new official method

  • A Sub-Committee of the Agricultural Education Association
  • Published online by Cambridge University Press:
    27 March 2009, pp. 123-144

  • In the summer of 1923, the Agricultural Education Association appointed a sub-committee to report on the present position with regard to the mechanical analysis of soils. This committee has now reported to the Association, which has adopted its recommendation that the former Agricultural Education Association method(1) of sedimentation in a beaker shall be replaced by one depending on the depth concentration relationship in a settling suspension. The reasons for this recommendation and the experimental work on which it was based will be of interest and use to soil workers generally. The salient features of the report have therefore been presented in the present paper, and an appendix of methods has been added. The full details of the official method will be published in Agricultural Progress, the journal of the Agricultural Education Association.

  • Studies in calcium-caseinogen equilibria, and their bearing on the secretion of calcium in milk. (preliminary paper.)

  • Norman Charles Wright
  • Published online by Cambridge University Press:
    27 March 2009, pp. 640-642

  • Two fundamental explanations have been advanced to account for the unequal distribution of electrolytes on either side of a cell membrane: the one bases the unequal distribution on the existence of a cell membrane of so-called selective permeability, by which the membrane is endowed with the property of presenting varying resistance to the passage of different ions; the other regards the unequal distribution as being due to the selective action of the cell constituents themselves. This latter theory regards the cell primarily as a system in which the distribution of electrolytes is governed by the equilibrium existing on either side of a membrane permeable to electrolytes but impermeable to other ionised constituents of the cell.

  • On the fertility of stallions

  • H. G. Sanders
  • Published online by Cambridge University Press:
    27 March 2009, pp. 466-491

  • Two sets of records, for Light and Heavy Horses respectively, have been analysed statistically, with the object of studying some of the factors which affect the percentage of foals left by a stallion in a service season.

    It has been found that the stallion himself is one factor, in that each individual’s percentage returns, in successive seasons, tend towards a constant figure; although there is every gradation, and even considerable variation from year to year, there are definitely good and bad “getters” of foals.

    A stallion's fertility varies according to the district of the country in which he stands or travels, being higher in the north and west of England and Wales than in the south and east, and very low in Scotland.

    In moderation, frequent use does not impair a stallion's fertility; there is, in fact, some (insignificant) evidence that the more mares he serves, the greater the proportion of foals he leaves.

    There is a slight tendency for a stallion's fertility to rise from the time he is 3 years old till he is 13 years old—this result may, though, easily be due to chance; on the other hand it is quite clear that fertility declines after the age of 16 years, and this occurs over the whole range, and is not caused by a certain number becoming absolutely sterile.

  • Alkaline milk and its detection by the brom cresol purple test—I

  • F. Procter, A. T. R. Mattick
  • Published online by Cambridge University Press:
    27 March 2009, pp. 145-148

  • During the past five years many appeals for assistance have been received at this Institute from cheesemakers in various parts of the country, who from time to time have found, themselves unable to secure satisfactory coagulation of their milk by rennet by reason of some abnormality which is not patent to the eye.

    Difficulties are also encountered in the liquid milk trade from causes which appear to resemble those which trouble the cheesemaker.

    In view of the necessity for detecting milk such as this, use has been made of di-brom-ortho-cresol-sulphon-phthalein or brom cresol purple, which indicates colorimetrically the reaction or hydrogen-ion concentration of milk, and provides a starting point for the further investigation of those samples of which the reaction is abnormal.

Front matter

  • AGS volume 16 issue 4 Front matter

  • Published online by Cambridge University Press:
    27 March 2009, pp. f1-f6
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Research Article

  • On the capillary forces in an ideal soil; correction of formulae given by W. B. Haines

  • R. A. Fisher
  • Published online by Cambridge University Press:
    27 March 2009, pp. 492-505

  • 1. The omission of the tension in the air-water interface has introduced an erroneous factor into Haines’ formulae; certain additional factors have also crept into his expressions for average stress.

    2. With these corrections, the stress due to moisture varies comparatively little with changing water content, though falling slightly throughout the range. The energy needed to cause rupture rises continuously in a manner not unlike Haines’ measurements, and should more probably be associated with them than should the tensile stress.

    3. The geometrical approximation used by Haines gives a close geometrical representation of the figure, but a mechanical approximation which is less satisfactory. Since neither the formulae connected with the true curve, nor the tables needed to use them, are readily, accessible, sufficiently exact numerical data have been here put on record.

Front matter

  • AGS volume 16 issue 3 Cover and Front matter

  • Published online by Cambridge University Press:
    27 March 2009, pp. f1-f6
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  • Ags volume 16 issue 1 Front matter

  • Published online by Cambridge University Press:
    27 March 2009, pp. f1-f5
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Back matter

  • AGS volume 16 issue 1 Back matter and Errata

  • Published online by Cambridge University Press:
    27 March 2009, p. b1
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Page 3 of 3