PART III. 

 COLLECTANEA. 



Art. L General Subject. 



Active Molecules. — Fifteen years ago. Dr. Drummond, now Professor of 

 Anatomy and Physiology in the Belfast Academical Institution, detected 

 these bodies in the choroid coat of a haddock's eye, and published an 

 account of the discovery, at that time, in his thesis De Oculi Anatomia 

 Comparativa. He described them as long and spicular, various in size, and 

 with the glitter of polished silver, so intense, that, when viewed in sunshine, 

 the eye could scarcely bear its brightness. Multitudes revolved continually 

 round their axis, while other and larger particles, after lying motionless for a 

 little time, described three or four semicircles, and then sank into their former 

 quiescence. These they repeated at short intervals, when they vanished to 

 reappear in the same spot after the lapse of two or three minutes. This sin- 

 gular movement was only observable in the larger corpuscles, the smaller 

 glittering in perpetual revolution around their axis. The motion could 

 not have proceeded from evaporation, for whether the fluid were com- 

 pressed between plates of glass, or covered with oil, it continued ; nor from 

 electricity, for neither attraction nor repulsion was exhibited ; nor from the 

 agitation of the water, for then the other molecules should have shown a 

 similar motion. " To suppose these particles," says the Doctor, " possessed 

 of vitality may appear repugnant to reason, but I can conjecture no other 

 way in which the phenomenon can be explained." The above-mentioned 

 thesis was published in 1814, and a more detailed account was given 

 in the Transactions of the Edinburgh Royal Society for the same year, in a 

 paper " On certain Appearances observed in the Eyes of Fishes ; " a title by 

 no means inviting, which may perhaps account for the little attention which 

 the communication received. 



To these spicula, as he afterwards ascertained, the metallic colour 

 of fishes is owing ; and to observe them in a very simple manner no- 

 thing more is necessary than to scrape some of the scales off a salmon or 

 herring, where the metallic or silvery tint is brightest; put them into 

 a wine-glass with a tea-spoonful or two of water, and stir them so that the 

 silvery film which is attached to the under surface of the scales may sepa- 

 rate. That film is composed of the moving spicula ; and when it has 

 whitened the water in the slightest degree, put a drop of the latter on any 

 black or very dark surface in the sunshine, the stronger the light the better, 

 and, with the naked eye, thousands of brilliant particles may be observed as 

 busy as motes in the sunbeam. In the microscope also the light must fall 

 on them ; for they seem to be very opaque, and it is only by reflected light 

 that they can be observed. — t 



Art. II. Zoology * 



The Cuckoo. — Sir, Reading what you say relative to the cuckoo in 

 your Magazine of Natural History, I beg to inform you that about fifteen 

 years ago I obtained a cuckoo from the nest of (I think) a hedge sparrow, 

 at Old Brompton, where I then resided. It was rather curious, as being 



