On the nature, locality and optical phenomena of muscae volitantes / by James Stark.

Date:
[1843?]
Catalogue details

Licence: Public Domain Mark

Credit: On the nature, locality and optical phenomena of muscae volitantes / by James Stark. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    particles of hair, or short tubes moving before the eyes. When tlie eye, however, was directed to the clear sky a very different appear- ance was presented. According to the clearness of the sky and the direction of the sun's light relative to the eye, these bodies appeared to be transparent or to have a slightly opalescent hue, or to consist of bodies with a clear centre surrounded by a bright halo, or with a dark centre and a luminous circumference, or they resembled little glo- bules of glass, or drops of dew, or pearls, and when they were in short broken lines they resembled short strings of pearls, or of glass beads. In some particular lights each particle seemed a moving spark, so that the appearance presented to the eye was as if a shower of sparks, with irregular shaped particles of fire, danced before the eyes. All these varied appearances were seen at one and the same time by alternately directing the eye to different parts of the sky and wall. All evidently depended on the varying action of the rays of light on some material particles which were the undoubted cause of musccE oolitautes. In other states of the eye the appearance resembled irregular wavy or zigzag lines ; but when these were minutely examined they were found to consist of the rounded particles above described, beino- thrown into strings or rows, in which state they often closely re- sembled fine transparent tubes, filled with globular bodies ; and wht re several of the globular bodies were heaped together, gave the idea of the tubes being thrown into a knot at that point. Whenever this peculiar cobweb or reticular appearance, as it may be termed, {vuus reliculalui) was observed, it was remarked that their motion was much slower than when the muscae consisted of irregular or round- ed detached particles. In some cases, indeed, this was perfectly remarkable, the reticulations or lines scarcely seeming to move till the movement of the eye itself caused them to assume new arrano-e- nients. When, however, motion was observed among the linesfit was frequently remarked that one portion of a line would break off, and fall slowly as a detached particle, leaving the other portions to descend more slowly. This fact, which was very frequently ob- served, showed the correctness of the observation, that every one of these lines was made up of accidentally agglutinated particles,—a fact rendered still more evident to the senses by moving the eye, which had the effect of destroying completely the old arrangement of the particles, and throwing them into new, but still linear forms. These lines, apparently according to the light admitted to the eye, presented all the varied colours above remarked, as being seen in the detached mvscce. It is well worthy of remark, however, that this varied mode of examination, viz. by presenting the eye alter- nately to a bright and to a darker portion of the sky and wall, sa- tisfactorily established the fact of all these apparent line^ beino' com- posed of more or less globular or rounded particles, agglutinated la- terally, and having little cohesion to each other. In a very bright light they resembled strings of pearls, or of glass beads, or little balls of fire arranged in strings. Sometimes the centre of each se- parate particle was dark, whilst the circumference was surrounded