IN approaching the consideration of the problems afforded by the arterial pressure in man, it is unnecessary to enter deeply into the history of the subject. Tigerstedt (1), Hill (2), Vaschide and Lahy (3), and Janeway (4) have fully analysed the voluminous literature which has grown up around it. It will be sufficient to mention the original experiment of Hales (5), in which the arterial pressure was measured by the height to which the blood rose in a vertical tube connected with the artery, and of Poisseuille (6), and Ludwig (7), who introduced and improved the method of estimating the arterial pressure by means of the mercurial manometer, which has since been modified by many subsequent observers. To obviate some of the disadvantages of the mercurial manometer, which will engage attention at a later stage, Chauveau and Marey (8), and Fick (9), almost simultaneously introduced elastic or spring manometers. These have undergone many alterations at the hands of numerous followers.

IT is a remarkable fact that in spite of the primitive features which appear to be preserved in the existing genus Lycopodium, there is little or no evidence pointing to ancient forms to which this genus itself can be related. Some of the smaller palæozoic Lycopodiales, impressions of which are named Lycopodites, may perhaps have been eligulate, homosporous forms, but in many of the better known examples they appear to have been heterosporous, and suggest comparison rather with Selaginella than with Lycopodium. In the course of a re-examination of the morphology and structure of Lycopodium cernuum, and a comparison of it with other species of Lycopodium, features of interest in the morphology of the cone were disclosed which indicated a remarkable similarity in plan of construction between this Lycopodium and the cone of Spencerites. A preliminary account of the cone of L. cernuum will be given here, leaving the consideration of the anatomy and the comparison with other species until the full account is published.

Of recent years a considerable amount of work has been done in measuring the electrical resistance of spark gaps under different conditions. The subject is important, both for its application to wireless telegraphy and on account of its bearing on the mechanism of the spark gap. Spark spectra are, as is well known, more complex than arc spectra. Formerly this was attributed to a very high temperature in the spark, but it is now regarded as due to a disintegration of the atom produced in the spark gap. Or, as Baly puts it in his book on Spectroscopy, in the spark gap the atom is in a state of assisted radio-activity. If the current density in the spark gradually increases until it is strong enough to disintegrate a particular system in the atom, we should expect a new spectrum to be produced then, and probably a change in the resistance of the spark gap. My experiments have shown me that our methods of measuring the resistance of spark gaps are not nearly accurate enough to show such a change if it existed.

(a) On the assumptions that resistance to deformation is due to simple friction, and that the coefficient of friction is independent of the load, the ratio of the yield point in tension to the yield point in compression, for what is ordinarily known as mild steel, is calculated as 2·384 to 3·384, or as 0·705 to 1. Experimental results so far obtained do not agree well with these figures, the value for the tensile yield point being relatively high, and that for compression relatively low.

(b) On the further assumption that a cohesive force acting between the metallic particles gives rise to a frictional resistance which may be added (algebraically) to that due to the effect of the external load, the value of this cohesive force is deduced as equal to 3·384 times the stress which corresponds with the tension yield point, or to 2·384 times that corresponding with the compression yield point. Experimental results from a large number of tests agree very fairly with the calculated figures for the case of tension.

In a recent paper (Zeitschrift für Electrochemie, 1906, page 265) Mr Maitland has redetermined with great care the electromotive force of an iodine solution with a platinum electrode against a mercury-calomel electrode. As, however, no observations seem to have been published of the electromotive force of iodine against iodine of different concentrations, it seemed advisable to determine those values before proceeding to the determination of the values for alcohol solutions.

1. RECENT experiments by Olszewski on hydrogen (Phil. Mag., May 1902), and on air and nitrogen (Phil. Mag., June 1907), have exhibited results which are not in accordance with theoretical deductions based upon Van der Waal's equation of state (Dewar, Proc. Roy. Soc, March 1904; Porter, Phil. Mag., April 1906; Hamilton Dickson, Phil. Mag., January 1908). An inversion temperature is not necessarily limited by the condition, which was satisfied in the porous-plug experiment of Joule and Kelvin, that the initial and final pressures should be nearly equal. In Olszewski's experiments that condition was widely departed from. Taking account of large differences of pressure, Dickson shows that Van der Waal's equation leads to the result that the inversion temperature must fall when the initial pressure increases, the final pressure being kept constant. Olszewski's experimental results are opposed to this conclusion; and Dickson suggests, as a possible cause of the discrepancy, an appreciable difference between the initial and final values of the kinetic energy. The following reasoning seems to indicate that such a difference would not alter the nature of the theoretical conclusion.

MANY attempts have been made to utilise electrolysis in aneurysms, especially in those thoracic ones that are not amenable to ordinary surgical treatment; it has been hoped that the clotting which occurs around the poles might serve as a nucleus for further coagulation and deposits of fibrin, and that the aneurysm cavity might in this way become partially filled up. Such attempts have not met with much success hitherto, and the purpose of this research has been to endeavour to determine by experiments on blood serum outside the body what the actual effect of electrolysis is so far as regards clotting. Various methods of electrolysing the blood in an aneurysm have been used by surgeons. Ciniselli introduced needles connected with both poles, and reversed the direction of the current every five minutes; of 38 cases so treated, 27 were ameliorated, but none were cured. In the unipolar method one pole only was introduced, and the other was connected with an indifferent pad placed in the vicinity. The difficult question was which pole to introduce. The positive pole gave the firmest clot, but it was thought that it might be difficult to withdraw, and that hæmorrhage or even rupture of the vessel might follow.

IN 1903 Heusler made the important discovery that alloys of copper, manganese, and aluminium are strongly magnetic. It was shown in the paper published by Heusler that by properly adjusting the amounts of the component metals present an alloy is obtained the permeability of which is comparable with that of cast iron. Heusler also demonstrated the fact that the properties of this alloy are profoundly modified by thermal treatment.

SPECIAL cases of the determinant

where u is a function of x, y, z, …, may well have appeared at a very early date in the history of determinants. The case where u=ax2+2bxy+cy2 may be viewed as traceable to Lagrange (1773), and the case where u=ax2+by2+cz2+2dyz+2ezx+2fxy to Gauss (1801); but it is certain that in those cases the elements of the determinants were not looked on as second differential-quotients of u. The general conception first occurred to Hesse in the year 1843.

WHILE studying the fossil Osmundaceœ several interesting points illustrating the origin of the leaf-trace were brought under our notice, which are exhibited with such exceptional clearness in Thamnopteris Schlechtendalii, Eichwald, sp., that they deserve especial recognition. The full discussion of the subject, however, is reserved until the publication of the next part of our memoir on the fossil Osmundaceœ.

The departure of the leaf-trace in Thamnopteris is typically protostelic. That is to say, the xylem of the leaf-trace first of all appears as a protuberance on the surface of the xylem of the stem (fig. 1).

THE minor fluctuations of the atmospheric pressure are now engaging the close attention of meteorologists, and my own attention has been drawn to them on account of their connection with the oscillations of lake-surfaces generally known since Forel's investigations under the name of seiches.

As these fluctuations often do not exceed a millimetre or two of water, they are not shown by the ordinary self-registering apparatus. In order to record them we may use a specially sensitive form of barograph, such as the Richard statoscope, which is delicate enough to show these small fluctuations, and yet can be brought back to a momentary zero whenever the indicator threatens to go off the scale or beyond the limits of safety. There are, however, two objections to this method of measurement.

THE subject of the “negative” viscosity of solutions has of late attracted considerable attention. Since the publication of the paper by one of us with Ranken in the Transactions of the Royal Society of Edinburgh, there have appeared a paper by Jones and Veazey, and two by Getman.

Since the latter of the papers by Getman contains a comprehensive review of the older literature on the subject, it is unnecessary for us to do more than indicate those points which are of fundamental importance. First noticed by Hübner in 1873, “negative” viscosity was observed by Sprung in the course of his extensive researches to occur in solutions of several potassium and ammonium salts, while corresponding sodium salts do not cause it. Later investigations added to the salts which are known to give rise to it; mention may be made of hydrobromic acid, in which it occurs at low temperatures but not at higher temperatures, whilst it does not occur at all in the case of hydrochloric acid.

DEATH under the administration of chloroform as an anæsthetic is an accident which, although fortunately rare, is well known to all; but the occurrence of a late poisoning, sometimes manifesting itself several days after the administration of the drug, is less well recognised. This too is rare, but its occurrence indicates the very profound effect which such a drug may exercise upon living tissues.

A very large amount of work has been done upon the immediate influence of chloroform upon the nervous system and upon the circulatory and respiratory mechanisms, but few observations on its more lasting effects upon the general metabolism have been recorded.

One of us (D. N. P.) has shown in the preceding paper that chloroform, when administered to dogs by the respiratory passages, may produce a purely stimulating action upon hepatic metabolism; whereas when it is given by the mouth, and to a less extent when it is given hypodermically, it exercises a distinctly toxic action, decreasing the activity of hepatic metabolism and leading to degenerative changes in the liver cells.

In attempting to find an explanation of these phenomena, it was necessary to know whether any difference existed in the distribution of the drug throughout the system after it had been given by these channels.

To elucidate this, the following series of observations were undertaken upon rabbits.

Ever since I have learnt something of the meanings of Grassmann's Ausdehnungslehre, and have at the same time learnt to regard the beauties of that system with something akin to awe, I have been persuaded that on the lines of Quaternion Algebra there is to be built a system very much like the Ausdehnungslehre, but an improvement thereon. Of course it will be matter for differing opinions whether what I call Multenions is really an improvement on the Ausdehnungslehre. I here record my own personal opinion that it is.

I do not suppose that anybody will maintain that a multitude of different kinds of multiplication within the bounds of one method can be regarded as anything but a blemish,—a blemish that may be justified by necessity and utility. The Ausdehnungslehre seems to me to have this blemish, and Multenions not to have it. Whether along with the absence of the blemish there becomes present an additional difficulty of manipulation is questionable. I have not found it so, but this may be due to the fact that I have so long been in the habit of thinking through the quaternion machinery.

I think these general remarks are all that can be usefully set down as a summary. The paper itself appears to be too condensed to admit of a true summary other than a mere table of contents.

The inca bone in the human skull is usually regarded as the homologue of the interparietal of some other mammals. The commonest or best-known form of the interparietal occurs in the rabbit as a single somewhat oval bone, its long axis being transverse, filling up a space between the parietals just in front of the line or curve of the occipital.

Carl Vogt (Lectures on Man, London Anthropological Society, 1864) makes frequent and detailed reference to a Helvetian skull. From the woodcuts, p. 52, fig. 15; p. 66, fig. 22; p. 70, fig. 26; p. 389, fig. 124; and p. 390, fig. 125, it is clear that a small round undivided bone occurred in this skull in a situation roughly corresponding with the position of the interparietal in the rabbit. I say “roughly,” because the posterior border of the bone in the Helvetian skull just touches the occipital at the lambdoid suture, while in the rabbit the interparietal for about half the extent of its perimeter is in contact with the occipital.

The middle cells are present throughout the whole length of the spinal cord. They are situated in the middle region of the grey matter, between the free anterior and free posterior cornua; but they sometimes also extend into the regions usually occupied by the anterior cornual cells, by the intermedio-lateral tract or by Clarke's column. The small cells in the base of the anterior horn (scattered cells) cannot be sharply separated from the middle cells, nor can most of the small cells about the base of the free posterior horn.

Although some of the middle cells may be found in all this wide area of distribution at practically any level of the cord, there are certain arrangements of cells which may be looked upon as typical of each segment, or at least of each region of the cord. In the upper cervical region they are not on the whole very abundant (this differs from Waldeyer's account), but are best developed in the central and para-central fields. In the cervical enlargement they are much more numerous, particularly within a broad band extending from the formatio reticularis to about the anterior grey commissure. Throughout the dorsal region they are again comparatively few in number, and may be scattered irregularly; but small groups are often found, most commonly in the central area, about on a level with the central canal, and in the post-central area, between Clarke's column and the reticular group of the intermedio-lateral tract. In the lumbar segments the middle cells are abundant, particularly centrally and in the base of the anterior horn. Their field extends anteriorly, until in the lower sacral region they come to be found over the whole area of the anterior cornua in addition to their more usual situations.

At all levels, as studied in serial sections, the distribution of the middle cells is seemingly erratic and casual. No regular plan of arrangement can be made out, and there is most certainly no segmentation (as Argutinski described) like that so well seen in the intermedio-lateral tract. The cells are sometimes just dotted here and there singly; sometimes they are scattered fairly thickly and evenly over the whole or part of the regions they are to be found in; or, again, they may occur more thickly in one part, or be aggregated into a distinct little cell group or nest, but even then these cell groups are seldom so closely packed as are the cell groups of the intermedio-lateral tract. The duration of any one of these types of cell arrangement is inconstant; and although there are levels where cells seem for a bit to be almost persistent in one place, this much can be stated as a general rule, that no middle cell group lasts through more than a very few serial sections. If traced further, the group is found either to shift to some other area or to die out altogether. Occasionally there appears to be a variation in number of cells parallel with the oscillations of the intermedio-lateral tract, but closer study shows that this is by no means absolute, and is probably only a local accidental variation.

Without expressing any opinion as regards function, I am inclined to divide the cells I have described collectively as middle cells into three groups, basing this division merely on the distribution and arrangement of the cells and on the microscopic appearances of the cell bodies. These divisions are, however, not very sharply defined either as regards the character of the individual cells or in the cell distribution. Still they seem to warrant such a division being made, and to suggest at least that the cells of the three groups may be functionally different. The groups I would make are—

(1) The middle cells proper, or central cells, occurring chiefly in the central area of the grey matter. These cells are of medium size and very similar to those of the apical group of the intermedio-lateral tract, multipolar, polygonal or rounded polygonal in outline, with a comparatively large nucleus and a few chromatic granules round it in the cell substance. Sometimes scattered, but more often present as a small clump of cells. With them may be included the cells in the para-central area, which, although sometimes forming a distinct and separate aggregation of cells, can mostly not be separated off from the central cells. Many of the cells occurring in the reticular area at levels where the reticular group of the intermediolateral tract is not present (especially in the lower cervical region) may probably also be included here.

(2) Anterior central cells in the base of the anterior horn—one of Waldeyer's “scattered” cell groups. As this name implies, these are often simply scattered over the area in question, but sometimes they are gathered into small cell-nests, but rarely very compact ones. Although there is no sharp boundary between them posteriorly and the central cells, they are in the main larger cells, and are further distinguished by their shape. They are not so often definitely multipolar and of approximately equal diameter in different directions, but more frequently appear to be bipolar, with longdrawn-out processes. The axis of elongation may be variously oriented. With these would fall to be included the middle cells in the external central area of the lateral enlargements, particularly in the lumbo-sacral cord. Possibly also some of the para-central cells should be classed with this group, and not with the previous one.

(3) Post-central cells. These lie in the area between Clarke's column and the formatio-reticularis, or in the corresponding region of the grey matter at level where Clarke's column is unrepresented. As with the anterior central cell, there is no sharp boundary between this series and the central middle cells. They are often continuous, or the cells may lie betwixt and between the two areas. But although many of the posterior cells may be as large, they are distinguished on the whole by being smaller in size than the central cells and less definitely polygonal, more rounded in outline. They are generally present either as a small clump or as a band of cells on the outer and posterior aspects of Clarke's column. Posteriorly, it is very difficult to separate this group from the posteriorbasal and posterior-marginal cells of Waldeyer. With this group may be included cells present in the area of Clarke's column, particularly when that column is absent or only represented by occasional cells. Also some of the small cells found in the reticular formation, especially those lying between (vertically) the nuclei of the reticular group of the intermedio-lateral tract.

These subdivisions may require modification from subsequent investigations, particularly by tracing the course and termination of the cell processes. I have attempted to do this by means of Cajal's silver impregnation methods, but, so far, have not succeeded. All I can affirm is that the fibres arising from the middle cells run in a variety of directions to begin with; but as some could be traced far enough to be seen doubling more or less sharply upon themselves, this gives no real clue to their destination. In no case could I follow any one to a termination. In some cells them was observed an endo-cellular fibrillary network, similar to that in the large motor cells of the anterior horn. In this particular cord the following figures give approximate average diameter of the cells of the different groups:—

In conclusion, I have to express my thanks to Dr Alexander Bruce for suggesting this subject for a thesis; to Dr Theodore Shennan, in whose laboratory the preparation of the sections was carried out; to Mr Henry Wade for the use of micro-photographic apparatus; and lastly to the Carnegie Trust, since this thesis is part of work done under the terms of a grant from the Trust for original research.

1. Nickel and the Heusler alloy give “sensitive states” of nearly 2 and about 5 per cent. respectively for a magnetising field of 8 C.G.S. units.

2. Steel wire specimens dropped vertically on a stone slab from a height of 1 metre showed a reduction of 37 per cent, in the “sensitive state” for a single fall, 49 per cent, for three falls, 62 per cent, for ten falls, and 73 per cent, for fifty falls.

3. After the “sensitive state” has been removed from a specimen by the process of demagnetising by reversals, it cannot be completely restored by reannealing. That is, the specimens exhibit a fatigue effect.

4. In the case of one variety of steel, the “sensitive state” had been reduced to less than one-half its original value after seven annealings, and to one-fifth after seventeen.

5. No recovery from the fatigue condition was observed in specimens which had been laid aside for fifty-four days.

6. Repeated annealings without intermediate magnetic testing showed neither an augmentation of the “sensitive state” nor a fatigue effect.

7. Specimens demagnetised at −190° C., heated to room temperature, and cooled again to −190° C., showed a small “sensitive state” at that temperature.

8. Larger effects were induced by heating from −190° C. to 15° C., or by cooling from 15° C. to −190° C.

9. A “sensitive state” could be induced by any variation of temperature, but not by exposure to a steady temperature, either high or low. The effect is associated solely with change of temperature.

10. The amount of “sensitive state” induced by equal temperature alterations varies with the position of the range on the temperature scale and with the material.

11. The change from the “sensitive” to the normal condition is unaccompanied by any appreciable change in the specific electrical resistance or elastic constants of the material.

The electrical conductivity of most glasses at a temperature of about 100°C is barely a measurable quantity.

For this reason, and on account of the fact that glass conforms to the general rule applicable to non-conductors in showing an increase of resistivity for a fall of temperature, this material has come to be regarded .as practically incapable when cold of allowing the passage of an electric current.

With a view to the further study of electrical conduction in glass, and also because of certain experimental advantages which a conducting glass would possess, I have endeavoured to produce a transparent vitreous substance having that property.

In a former paper (Proc. R.S.E., 1905) an investigation was given of the magnetic properties of the closest packed homogeneous cubic arrangement of molecular magnets, and it was found that the results were in good agreement with the observed properties of crystals of magnetite. It was also suggested that a parallel investigation of other cubic arrangements might lead to a discrimination of molecular arrangement, so far as the magnetic constituents are concerned, in actual crystals. To settle this point, if possible, the present investigation was undertaken.