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SUPPLEMENT 



examined by the aid of the microscope, it will 

 be found to be composed of concentric strata 

 or layers, somewhat resembling the coats of 

 an onion. One of these laminae separated, 

 and placed under a powerful microscope, will 

 be seen to consist of flat fibres or bands, aris- 

 ing from each pole of the globular lens, and 

 expanding towards the equator, like the spaces 

 between the meridians on the artificial globe. 

 The edges of these fibres are serrated, and 

 fit into each other like the teeth of a double 

 rack, or the sutures of the human skull." 

 " When the power," observes Sir D. Brews- 

 ter, "is small, or the microscope not good, or 

 the laminas too thick and riot nicely detached, 

 each row of interlocking teeth appears as a 

 dark line, sometimes as sharp as a black line 

 drawn upon paper with a pen. Sometimes 

 the lines appear rough and ragged, and as 

 the fibres become less in approaching the 

 poles, the black lines are as difficult to resolve 

 into teeth, as the lines on test objects. The 

 following measures will show what a wonder- 

 ful structure in the eye has been disclosed to 

 us by the microscope. The calculations refer 

 to the lens of a cod, four-tenths of an inch in 

 diameter. 



Numbe of fibres in ench laminae, . 2500. 



Numbe of teeth in each fibre, . . 12,500. 



Numbe of teeth in each laminae, . 31,250000. 



Numbe of fibres in the whole lens, . 5,000,000. 



Numbe of teeth in the lens, . 62,500,000,000. 



Or the lens of a cod contains five millions 

 of fibres, and sixty two thousand five hundred 

 millions of teeth ; and if we reckon the curved 

 end of the tooth as one surface, each tooth 

 will have six surfaces, which come into 

 contact with the corresponding surfaces of (he 

 adjacent tooth, so that the number of touching 

 surfaces will be three hundred and seventy-five 

 thousand millions, and yet this little sphere of 

 tender jelly is as transparent as a drop of the 

 purest water, and allows a beam of light to 

 pass across these almost innumerable joints, 

 without obstructing or reflecting a single ray." 

 We have here given Sir D. Brewster's des- 

 cription verbatim ; but we must enter our pro- 

 test against the system of wonder-making, 

 into which it appears even this eminent philoso- 

 pher can occasionally fall. No useful end 

 is obtained by entering into minute numeri- 

 cal details, of which the human mind can con- 

 jure up no idea ; this practice prevailed with 

 the early micrographers, and the consequence 

 was, that their writings fell into neglect, and 

 ultimately excited little attention, except from 

 those who delighted to number the repetitions 

 of a letter in the Bible, or to resolve the vast 

 bulk of the ocean into separate drops of wa- 

 ter. It is this practice, and it only, that has 

 caused a distaste for microscopic inquiry, and 

 exhibited it as a puerile pastime which should 

 give place to loftier pursuits. Let all the 



wonders of the minute world be unveiled; but 

 let this be done without ridiculous exaggera- 

 tion or valueless precision. The microscope 

 will never be other than a childish toy, so 

 long as the observer's aim be rather to bewil- 

 der than to inform the popular mind. We 

 have deemed it right to make these observa- 

 tions, at a time when the instrument is ap- 

 proaching, possibly, to its highest perfection, 

 and when, in the words of Dr Goring, " a 

 new and golden age of observation may be 

 expected to commence." 



The nature of the blood, and Us circulation 

 through the veins and arteries of animal bo- 

 dies, can be thoroughly understood only by 

 microscopic observation. " When Dr Har- 

 vey made his grand discovery of the circula- 

 tion of the blood, and first lectured upon it in 

 St Bartholomew's hospital in 16 19, he was 

 ridiculed, and lost his practice through main- 

 taining what was then supposed to be so ab- 

 surd and wild a theory. The idea was sug- 

 gested to his mind by reflecting on the valves 

 of the heart and veins, which were evidently 

 so planned as to allow a fluid to pass but one 

 way. All the philosophical reasoning, how- 

 ever, of this celebrated man, could riot esta 

 blish what appears to us so plain a truth, un- 

 til it was evidenced in the circulation of cold 

 blooded animals by means of the microscope, 

 and thus placed beyond a doubt. Discerning, 

 as we can do, the very forms of the globules 

 of that fluid, as they flow through the capilla- 

 ries from the arteries to the veins, in obedience 

 to the laws impressed upon them by the A\ 

 mighty Creator viewing this sublime phe- 

 nomenon, by which life itself is diffused 

 throughout, and sustained in every part of (he 

 system, who can resist conviction of the 

 great truth?" The same eloquent writer (Mr 

 Pritchard,) observes in another place : " The 

 globules of the blood may be seen passing ra- 

 pidly along the capillary ends of the arteries 

 into those of the veins, where the intervening 

 member is sufficiently diaphanous, as in the 

 ear of the young mouse, the fins and tail of 

 the carp, gold-fish, stickle-back, tadpole, and 

 of most small fish; and in the web between 

 the toes of the frog, lizard, eft, &c. In the 

 arachnoida, (spider tribe,) at the joints of the 

 legs, I have observed the circulation very dis- 

 tinctly, the current of dark globules passing 

 rapidly at each pulsation of the dorsal vessel. 

 In the antennae and wings of terrestrial in- 

 sects, it has also been seen when they have 

 just emerged from (he chrysalis, as in the 

 perla viridis and semblis bilineata. In several 

 aquatic larvae and small Crustacea, the circu. 

 lating fluid traverses the limbs, antennae and 

 tail, and thence moves along the dorsal vessel 

 towards the head, and down the sides of the 

 body, in cavities, and not distinct vessels j 



