with and without calcic chloride). The chief proteid, however, appears to be of the nature of nucleo-albumin (Halliburton's sodic-chloride method). Mucin is present in variable amount, and originates from the glands of the gullet below the crop. These glands enlarge and become more active during the feeding of the young.

The young pigeon is, then, fed at first upon a highly nutritious food, whose solids consist in the main of nucleo-albumin and fat. The explanation of this peculiar process lies in all probability in the fact that since pigeons rear so many broods in a season the young must be brought forward faster than could result from mere grain feeding, and hence a magnificently nutrient diet is supplied. When a cock or hen in milk' is separated from the young the involution of the crop changes occurs with great rapidity, for within twenty-four hours the temporary 'sebaceous glands' are loosened and cast off, the hypertrophied papillae which lie between them being subsequently reduced. Such birds swallow their own milk;' their villi contain more fat than normal birds, and fatty leucocytes are seen in abundance in the blood.

Some days, however, after separation, though the gross changes in the crop membrane have disappeared, fatty cells are found in the epithelium.

The 'milk' in the crops of such separated birds is also in finer particles than norinal and poorer in solid constituents.

A few quantitative analyses, kindly made for me by my colleague Mr. F. J. Hambly, are appended :

Milk % Solids % Milk % Solids % Milk % Solids % Milk Solids

7. On the Structure of Striped Muscle. By Professor J. B. HAYCRAFT.

The cross-s ss-striping of muscle is due to the form of the fibril and not to its internal structure. The fibril is like a beaded rod, and the striping is the optical expression of this. The proof of this is obtained by stamping moist collodion with a piece of muscle. The collodion stamp preserves the form of the fibrils, and shows identically the same cross-striping to the minutest detail. The stamps and their photographs were demonstrated. In one a fibril had been stamped in which one part alone was in the condition of contraction, and every detail of the striping, both in the relaxed and contracted conditions, was identically reproduced.

TUESDAY, AUGUST 14.

1. A joint meeting with Section A was held to discuss the following Papers by Professor Oliver Lodge, F.R.S.

A.-Experiments illustrating Clerk Maxwell's Theory of Light,
B.-An Electrical Theory of Vision.

The following Papers were read :—

2. On a Modification of Golgi's Methods. By OLIVER S. STRONG, of Columbia College, New York.

Golgi's methods may be divided into two principal heads: (1) The sublimate method, consisting essentially of hardening in bichromate of potash followed by immersion in bichloride of mercury. This method need not be further noted here.

(2) The silver methods, consisting of (a) the long, or slow, method, consisting of hardening for about twenty to thirty days in potassium bichromate followed by immersion in a solution of silver nitrate. (b) The rapid method, where the hardening is done in a mixture of bichromate and osmic acid. This is the method, slightly modified, which is so extensively used, and is the method used by Ramón y Cajal. (c) What may be designated the mixed method, or combined method, and consists in hardening first for a few days or a week or so in potassium bichromate, then a day or two in the osmium-bichromate mixture, and finally the immersion in the silver bath.

The rapid method is the best yet discovered for work on the peripheral terminations of nerves and for the embryonic central nervous system. For adult brains it is not so well adapted owing to the poor penetration of the osmic acid, and consequent liability to overharden the periphery while the central portions of even small pieces remain untouched. Moreover, adult brains are not well adapted for the study of the nervous or axis cylinder prolongations of the cells, owing probably to their sheath, so that on such material study by these methods would be chiefly directed to the cell bodies and their protoplasmic expansions. For such purposes the long Golgi method is eminently adapted.

While the long Golgi method avoids the disadvantages, including the expense -no small consideration where such quantities are used-of osmic acid, it has the disadvantage of requiring about a month, besides the uncertainty common to all these methods.

In order to reduce this period of time, and yet to avoid the use of osmic acid, the new method here proposed for the study of adult brains is the use of bichromate of lithium instead of the bichromate of potassium, with the same percentages. I have found that tissues (small pieces) placed in the former reach the favourable stage of hardening for the silver impregnation in the course of one to two days, instead of twenty to thirty days. It passes through this favourable period quite rapidly, but the whole process is reduced to such a short time that it is rendered much less tedious. The pictures yielded by this process, judging from the few made thus far, are certainly fully equal to those prepared by the other methods.

The subsequent treatment is as in the other methods, i.e., the piece of tissue is rinsed in strong alcohol, cut free hand or gummed on a block without any imbedding, and cut with a microtome. The sections are washed in several changes of strong alcohol, cleared in oleum origanum Cretici, washed briefly in xylo!, and mounted in dammar or Canada balsam, thinned with xylol, without a cover slip.

It would be interesting to ascertain how well adapted this new hardening reagent would be for preparing the central nervous system for other methods of staining, e.g., the Weigert method.

3. On an Attempt to supply Motor Power to the Muscles of the Larynx from a New Source. By Veterinary-Captain F. SMITH, F.R.C. V.S., F.I.C., Army Veterinary Department, Aldershot.

The subject used in these observations was the horse, the inquiry having in view the possible relief of the respiratory distress so common in this animal as the result of laryngeal paralysis.

The new source of nerve supply was sought for in the spinal accessory. The

recurrent and spinal accessory were exposed and divided, and the proximal end of the accessory was sutured to the distal end of the recurrent.

The only convenient test which could be employed to ascertain what progress the animal was making after the operation was that afforded by galloping it.

In one case, a few months after the above nerves had been united, there was only a slight harshness in the breathing during inspiration, even when the horse was severely pressed;' whereas, unless nerve impulses were passing down the accessory and through the recurrent to the larynx, the animal should have suffered from intense dyspnoea, as the whole of the dilator muscles of one side of the larynx would have been paralysed.

In a second case, the recurrent, before suture to the accessory, was known to have been degenerated for at least two years. This animal continued to have noisy breathing up to the time it was destroyed (twelve months after the operation), but it was unaccompanied by distress.

In the first case only an ordinary post-mortem examination was made to ascertain whether the nerves were united; in the second horse the nerves were stimulated electrically immediately after death, and a careful microscopical examination of the parts made.

On stimulating that portion of the recurrent in connection with the larynx the muscles actively responded; on stimulating the accessory well above the nodule uniting it with the recurrent, the muscles of the larynx again actively responded.

These observations were repeated several times by Professor Delépine, of Manchester (who kindly associated himself with me as an independent observer in the post-mortem examination), and the results are beyond doubt.

The muscles of the larynx of the above case, supplied by the accessory. recurrent nerve, were smaller and decidedly paler in colour than the healthy ones on the opposite side; on directly stimulating the muscles every portion of them actively responded to a weak current.

Professor Delépine examined the united nerves microscopically, and found in the recurrent between the point of union and the larynx small bundles of medullated nerve fibres and an amount of epi- and peri-neurium larger than normal. The place occupied by the old funiculi was quite distinct, but the nerve fibres occupied only a portion of the spaces thus indicated. The nerve fibres were all of smaller diameter than normal; most of them had a very thin myelin sheath which stained well with osmic acid. Professor Delépine was of opinion from this and the other observations that partial regeneration had certainly taken place, and that regeneration was progressing at the time of death.

By the tests employed it was not possible to say whether co-ordination of the laryngeal muscles occurred, but it is proposed in future observations to examine closely into this subject, and employ the laryngoscope to ascertain whether the impulses to the larynx are sent at the right moment.

At present it would almost appear to be possible to educate a nerve centre to perform a duty it was never intended for.

4. On the Causes and Prevention of Suffocation in Mines. By J. S. HALDANE, M.A., M.D., Lecturer on Physiology, University of Oxford. Evidence was brought forward by the author that most of the deaths caused by colliery explosions and fires in the workings are due to suffocation, so that a thorough instigation of the subject is of great practical importance.

He concluded that poisoning by carbonic acid is never the cause of death in cases of suffocation by choke-damp, black-damp, or after-damp; that deprivation of oxygen is always the cause in the cases of choke-damp or black-damp, and usually the cause in the case of after-damp, although after-damp, even when much diluted, is sometimes poisonous from the presence in it of products of in

complete combustion, such as carbonic oxide or sulphuretted hydrogen. He also discussed the effects of white-damp, and drew attention to the exceedingly poisonous character of the gases from the explosion of blasting powder.

In conclusion he described and exhibited a portable apparatus for enabling miners to escape through an atmosphere of after-damp to the fresh air in the neighbourhood of the shafts, and for rescue purposes.

5. Observations on the Effects of After-damp.

By J. SHAW LYTTLE, M.D.

The writer gave a detailed account of the symptoms presented by those who were found alive after the recent explosion at the Albion Steam Colliery.

6. Experiments on Memory. By W. G. SMITH, M.A., Ph.D.

If we examine any case of ready and accurate recollection taken from our daily experience, we find it difficult, if not impossible, to say how much of this accuracy is due to such factors as the interest which the experience aroused, the attention which we paid to it, the amount of effort and time spent during the experience. The following experiments were carried out with the view of trying to isolate experimentally the process of attention, and showing what changes in recollection occur when various kinds of distraction of attention are introduced. The experiments were begun in the Institute for Experimental Psychology in Leipzig, and have been carried on in the Physiological Laboratory in Oxford.

After a considerable number of preliminary experiments had been made, the following method was adopted. Twelve letters of the alphabet, arranged in such a manner that intelligible words or interesting ideas should not readily be suggested, were written upon a card, so as to form three lines. The card was shown to the reagent, who then tried to learn what was written on it. In each new experiment a new combination of letters was employed. By making a sufficiently large number of observations with different persons, one can eliminate to a considerable extent the fallacies arising from varying difficulty or familiarity of the combinations employed. The card was shown in every case for ten seconds, and the reagent was required, either immediately after he ceased to see the card or after an interval of about two seconds, to reproduce as much as he could remember of what he had seen.

A distinct and at the same time fairly simple form of distraction was secured by making the reagent repeat the series 2, 4, 6, 8..., or more rarely 3, 6, 9... while he was learning the letters on the card. In order that the person in charge of the experiments might have an effective control over the activity of the reagent, the series had to be repeated aloud, and each step in the addition was made to coincide with the stroke of a metronome going at the rate of sixty to seventy beats per minute. In order to compare the results of this form of distraction with those gained where the vocal organ was employed, but the mental effort involved was very small, the reagent was next required while memorising to repeat aloud with each beat of the metronome an unintelligible syllable, e.g.. 'la.' This form of distraction was further compared with that caused by activity of another set of muscles, viz., those employed in tapping the table with the forefinger, each tap coinciding with a beat of the metronome. Lastly, experiments were carried out to show the effect of memorising without any distraction save that due to the fact that the metronome continued to beat. These four variations were given in varying order one after the other, and were so arranged that 8, 12, 16, or 20 experiments were made in one hour.

In calculating the value of the results two methods were applied. The first resembles that employed by Münsterberg (Beiträge zur experimentellen Psychologie'), and consists in summing up the errors committed in reproducing the letters written on the card. The errors were classified as follows:-(1) Oission of a letter; (2) insertion of a wrong letter; (3) displacement of a letter or repro1894. 3 G

duction in wrong order. According to the second method, which resembles that commonly employed in estimating the value of answers to examination papers, a greater value is assigned to letters according as they correspond more exactly to what was written on the card. A letter which was given in a wrong position or without any hint as to its position had the value 1 attached to it. When a certain imperfect knowledge of its position was present, as when it was located in the right line or in the right order in a group of letters whose correct position was unknown, the value 2 was given. Each letter counted 3 when everything was correct. Letters wrongly inserted were disregarded. From an analysis of the results given by the first method it appeared that the number of insertions does not vary very much, and only in a few cases has an important influence on the results.

All the results of over five burdred experiments made with nine observers have been analysed according to the two methods, and the results agree except in a few

cases.

The general conclusion is that the memory is worst when the reagent performs the simple sum in addition (1); it is better when the distraction is caused by exercise of the vocal organ (2); that caused by movement of the forefinger (3) does not make the recollection much worse than it is when the observer is not distracted at all (4). This statement holds good with only a few exceptions for every reagent, and is confirmed by the subjective observations given in reply to the questions which were frequently asked. The average of the results given by the nine persons who assisted in the experiments is as follows: the upper line gives the values according to the first method, the lower the values according to the second method of calculation

An analysis of the errors shows that the curve of errors of omission follows closely that of the total number of errors: the other two kinds of error are much less numerous, and do not show any very important variation. A detailed analysis of the results, together with a discussion of their meaning and value, will be given in a future number of Mind.

7. On Typhoid Bacilli in Water. By Dr. L. OLIVIER.

WEDNESDAY, AUGUST 15.

The following Papers and Report were read:

1. On some Physiological Effe of the Passage of Rapidly-alternating Currents of great Intensity through Nerve. By Professor OLIVER LODGE, F.R.S., and Professor F. GOTCH, F.R.S.

2. On a New Spring Kymograph and Polyrheotome.

By Professor T. W. W. ENGElmann.

3. On the Production with the Capillary Electrometer of Photographic Records of Currents produced by Speaking into a Telephone. By

G. J. BURCH.

4. Report of the Committee on the Structure and Function of the

Mammalian Heart.-See Reports, p. 464.