In the majority of the processes with which one is concerned in the study of the medical sciences, one has to deal with assemblages of individuals, be they living or be they dead, which become affected according to some characteristic. They may meet and exchange ideas, the meeting may result in the transference of some infectious disease, and so forth. The life of each individual consists of a train of such incidents, one following the other. From another point of view each member of the human community consists of an assemblage of cells. These cells react and interact amongst each other, and each individual lives a life which may be again considered as a succession of events, one following the other. If one thinks of these individuals, be they human beings or be they cells, as moving in all sorts of dimensions, reversibly or irreversibly, continuously or discontinuously, by unit stages or per saltum, then the method of their movement becomes a study in kinetics, and can be approached by the methods ordinarily adopted in the study of such systems.

It has been known for the last thirty-four years that when the fresh excised eyeball of a frog is connected by non-polarizable electrodes with a sensitive galvanometer, an electrical current (travelling through the eye from the retina to the cornea) may be detected, and that variations occur in this current, due solely to the action of light on the retina.

It is also well known that salts of radium are luminous in the dark, and that if a tube containing radium† is pressed against the closed lid of the eyeball, or even pressed against the temple, one has the consciousness of luminosity. This being so, it was of interest to ascertain whether this luminosity was due to the radium causing fluorescence of any of the structures of the eyeball, or whether it was due to the direct action of one or other of the emanations of radium on the retina itself.

The quality of the human voice depends on the same laws as those determining the quality, klang-tint, or timbre of the tones produced by any musical instrument. Tones of a mixed character, that is to say, composed of a fundamental and partials, are produced by the vibrations of the true vocal cords, and certain of those partials are strengthened by the resonance of the air in the air-passages, and in the pharyngeal and oral cavities.

So strongly may certain of these partials be reinforced, as to obscure or hide the fundamental tone, and give a peculiar character to the sound. These, however, are only general statements, and there are still many difficulties in the way of a true interpretation of voice-tones. In the first place, we observe that we may sing a scale, using one sound for each note, such as la, la, la, etc. Or, by putting the mouth in a certain position, we can pronounce the so-called vowels, a, e, i, o, u (ou as the u in prune), uttering the sounds ah, ā, ē, o, ou. As we do so, we notice that each sound appears to the ear to have a pitch of its own, different from that of the others.

1. Since I had the honour of showing the phonograph to the Royal Society of Edinburgh, at a special meeting in November 1894, the instrument has occupied a good deal of my time and attention, and I now venture to give the general results of the investigation.

2. The instrument chiefly studied has been the machine used in this country known as the “Commercial Phonograph.” Any records taken by myself have been obtained with the ordinary apparatus forming part of the “commercial” speaker arm, but I have always reproduced these with the aid of the so-called “musical” arm. The commercial machine, or, to give it a better name, the English model, is so geared that the wax cylinder, inch (197 mm.) in circumference, makes two revolutions in one second, while the spiral grooves described on the cylinder are inch (⅛ mm.) apart. A spiral line about 136 yards in length may be described on the cylinder, and the recording or reproducing point travels over this distance in about six minutes.

3. I have also used the American model, which resembles in all essential particulars the one just described, except that the grooves on the cylinder are inch (¼ mm.) instead of .

There are several well-known methods of mixing colours, such as the superposition of two spectra or of different parts of the same spectrum—the method of reflection, Czermak's modification of Schemer's experiment, the use of rotating disks having coloured sectors, and the direct mixture of coloured powders or coloured liquids. In all of these cases the effect may be seen with one eye, and is due to the action of light on a definite portion of one retina. But may sensations of mixed colours be produced by binocular vision of the components ? Regarding this question various well-known observers have arrived at completely opposite results.

During the past two months my attention has been directed to the telephone, chiefly as an instrument which illustrates in a remarkable way the delicacy of hearing. As some of these experiments are novel, and may possibly assist those who are investigating the physical phenomena of the instrument, I beg to give a short account of them to the Society. To save circumlocution in description, the term “proximal” will be applied to the telephone receiving the stimulus, and the term “distal” to the one at the other end of the arrangement. Thus, if A talks to B, A will use the proximal, and B the distal telephone.

Since the date of the first communication, we have endeavoured to obtain quantitative results involving time as a variable element in the case of the action of light on the retina and optic nerve, We have therefore found it necessary to construct a true graphical representation of the variations of the electro-motive force occasioned by the impact and cessation of light. It is clear that to register minute galvanometrical alterations, the only plan that could be employed would be to photograph on a sensitive surface, covering a cylinder rapidly revolving on a horizontal axis, the alteration of position of the spot of light reflected from the mirror, just as continuous magnetic observations are registered.

Certain individuals appear to be incapable of appreciating musical sounds. They cannot distinguish one melody from another; and if by many repetitions of the melody in their hearing, they at last appear to know it, the addition of one or more of the parts of the harmony again renders the music unrecognisable to them. The question naturally arises, Is this defect owing to any peculiarity in the structure of the internal ear of persons so constituted which prevents them hearing certain sounds, or is it to be referred to the condition of the brain? On the other hand, many have what is termed a “fine ear,” by which we understand the faculty of appreciating, remembering, and, in some cases, of successfully imitating musical sounds. Have those individuals the organ of hearing more delicately developed?

The authors of this communication have more especially directed their attention to the problem of the specific effect produced on the retina and optic nerve by the action of light. Numerous hypotheses have been made from time to time by physicists and physiologists; but up to the present date, our knowledge of the subject is without any experimental foundation. For example, Newton, Melloni, and Seebeck, stated that the action of light on the retina consisted of a communication of mere vibrations; Young conjectured that it was a minute intermittent motion of some portion of the optic nerve; Du Bois-Reymond attributed it to an electrical effect; Draper supposed that it depended on a heating effect of the choroid; and Mosier compared it to the action of light on a sensitive photographic plate.

A systematic investigation into the physiological action of ozone, so far as we are aware, has never been undertaken. Isolated observations have been made by many while engaged in the examination of its physical and chemical properties, which have chiefly tended to show that it acts as an irritant on the mucous membrane of the respiratory tract, and they have also observed the peculiar odour which it excites by its effect on the organ of smell, from which the name ozone originated. Beyond this little has been attempted.

Since the date of our last communication, we have continued our investigations, with the following results:–

1. The light from a beam of uncondensed moonlight, though of weak intensity, and almost entirely free from heat rays, is still sufficient to alter the electro-motive power of the nerve and retina.

2. We have examined the phenomenon in the eyes of the following animals:—(1.) The common newt (Triton aquaticus). (2.) The gold-fish (Cyprinus auratus). (3.) The rockling (Motella vulgaris). (4.) The stickleback (Gasterosteus trachurus). (5.) The common edible crab (Cancer pagurus). (6.) The swimming crab (Portunus puber). (7.) The spider crab (Hyas coarctatus). (8.) The hermit crab (Pagurus Bernhardus), and (9.) The lobster (Homarus vulgaris).