Final yield of grain and straw reflect, or are functions of, the combination of processes conveniently designated “growth.” A successful analysis of “growth” would afford an analysis of “yield” and it is quite patent that “yield” must continue to be imperfectly understood so long as growth remains unanalysed. But although the full solution of the “yield problem” thus rests with plant physiology, it seems within the bounds of possibility that comparative studies upon varieties may bring to light distinctive (varietal) features of “growth” which are correlated with distinctive (varietal) features of “yielding power.” One or more of these may possibly serve as an “index” of yielding power, as the touchstone which is so urgently needed in plant breeding. The reliability of comparative studies of this kind rests fundamentally upon accuracy of “sampling.” For all the experimental attributes of freely tillering cereals, sampling is extremely difficult and the difficulties are most acute for “weight” attributes. Clearly then, a test of accuracy of sampling at all stages of growth is an indispensable preliminary. It was this consideration that determined the lines of the investigation to be recorded here and it is in the light of it that the results will be discussed.

The effects of food ingestion on the total energy exchange of man and of the dog have been fairly completely worked out. Lavoisier was the first to show that the oxygen absorption and carbon dioxide production were increased by ingestion of food. Rubner, in addition to confirming these observations of Lavoisier, showed that the heat given off from the body after food was equal to the heat evolved from the foodstuffs actually oxidised within the body and thus established the agreement between direct and indirect calorimetry. He showed, further, that the increase in heat production was greatest after protein food. This specific effect of protein food he designated the “specific dynamic action.” The work of Rubner has been continued by, amongst others, Magnus-Levy, Benedict, and Lusk. The latter showed that the specific dynamic action of proteins is due to the special stimulating effect of certain amino-acids on the tissues and that the increased heat production after fat and carbohydrate ingestion is due to plethora of oxidisable molecules round the living body cells. Recently Wood and his school (1) have carried out investigations on the metabolism after food in pigs.

The post absorptive state commences in the ruminant between 42 and 48 hours after the last food. If food is ingested before this time it becomes mixed with that already in the rumen and its decomposition by fermentation is thereby accelerated. The metabolism at 15 hours after the last food is about 23 per cent, above that in the post absorptive state. For about 36 hours after th commencement of the post absorptive state the R.Q. remains below that of fat oxidation and fermentation gases still continue to be excreted. Keasons are suggested by way of explanation for these phenomena in the causation of which absorption of gas from the rumen does not appear to play any appreciable part.

1. The mechanical analysis of a number of soils, clays, and other granular materials has been carried out by the writer's method and the results have been set out in the form of curves showing the relationship between summation percentages and logarithm of settling velocity.

2. The curves obtained are smooth. This suggests that all the necessary information as to the mechanical composition of a material can be obtained by using a relatively small number of experimental points and drawing the appropriate curve. Results obtained on one scale can readily be transferred to another scale by interpolation.

3. The most common type of curve is a sigmoid. The steepest portion of the curve represents the fraction present in greatest frequency. This has been termed by the writer the modal fraction. Two sub-types were found. In the case of certain heavy clays, the modal fraction appears to be at the lower end of the curve, whilst in the case of materials mechanically disintegrated the modal fraction is at the upper limit of particle size.

4. Composite curves are obtained in certain cases. They may represent mixtures of different materials, or soils in the earlier stages of formation from rock.

5. The lower limit of particle size appears to be represented by log in the case of normal soils and clays. In the case of certain finely divided but non-plastic materials, the lower limit appears to be in the region of . It is suggested that a better picture of the properties of soils would be obtained by taking the limit for clay at this poiDt instead of at log .

6. The use of the logarithm of settling velocity as a measure of particle size is discussed and it is suggested that the use of negative logarithms might be avoided by using log (v × 107), for which the symbol Lv is proposed.

In the above I have shown the result of a series of measurements of the hydrion concentration in milk, cream, buttermilk and whey, partly employing Biilmann's Quinhydrone Electrode, partly Höber-Hasselbalch's Hydrogen Electrode.

The results of the tests agree.

Measurements have also been made in fresh and heated milk.

By these measurements I found no difference in the reaction or buffer action of the fresh and heated milk.

The Höber-Hasselblach method is rather slow. This is unfortunate as the reaction of the dairy products (especially whey) is apt to change when kept standing, even for a short time. By this method one also runs the risk of too high pH values owing to loss of carbon dioxide and it is therefore far from being an ideal one.

Biilmann's Quinhydrone Electrode is quick working, easy and simple and you avoid the above-mentioned sources of error. It is therefore to be preferred for measurements in the fluids in question. It is especially well adapted for titrations, as it makes possible a large number of measurements in a short time.