G04 



SUPPLEMENT. 



bird, whether we regard the material of which 

 it is wrought, the elegance of its several parts, 

 or the admirable dependency of those parts 

 on each other. A feather consists of three 

 distinct parts the quill, the stem, and the 

 fibres that clothe the stem on each side. The 

 quill is at once the root of the structure, and 

 a reservoir for the nutriment required to sus- 

 tain it. The stem is the tree trunk ; and the 

 literal fibres are the branches which it puts 

 forth. When we examine one of these fibres 

 microscopically, we find smaller fibres arranged 

 along its edges ; and if these last be subjected 

 to a very deep power, we discover that they 

 are, in like manner, fringed with fibres cor- 

 respondingly minute. The most delicate 

 filaments of the feather exhibit a hair-like 

 structure, being composed of cups inserted one 

 within another ; or they present the appear- 

 ance of a jointed cane. The last named pecu- 

 liarity is illustrated in plate 34, fig. 8, which 

 shows an exceedingly minute filament of fea- 

 ther down as it appears under a linear magni- 

 fying power of 300. The exquisite finish of 

 the joints is very remarkable. We shall offer 

 only one general illustration of the structure 

 of feathers, selecting our specimens from the 

 delicate plumage of the humming-bird, as ex- 

 hibited and detailed in plate 34, figs. 26, 31, 

 34, 35, 36. Before entering into a descrip- 

 tion of these objects, we step aside to notice a 

 remark by Mr Pritchard on the hair of the 

 bird-catching spider of South Amercia(-fl/zc;-0- 

 scopic Objects, pi. 9.) " That taken from the 

 palpi is branched, and towards the extremity 

 the central stem enlarges, becomes fluted, and 

 assumes a bright orange colour. The use of 

 this augmentation in bulk towards the end is 

 not ascertained ; but I may remark that a 

 similar structure, on a larger scale, may be 

 observed in the small feathers from the breast 

 of the Indian humming-bird." Now from 

 observing a number of these feathers in dif- 

 ferent stages of developement, the writer was 

 enabled to ascertain the real character of the 

 formations to which Mr Pritchard alludes ; 

 and the reader will, we think, be disposed to 

 admire their singular use and remarkable 

 structure. Figs. 31 and 35, are perfect fea- 

 thers, about one-tenth of an inch in length ; 

 the latter exhibits the orange-coloured " en- 

 largements" just named and a number of 

 downy fibres of a pearly-gray tint. It forms 

 a most beautiful opaque object for the micro- 

 scope ; the rich colour of the pods contrasting 

 very pleasingly with the other parts of the 

 feather. Fig. 34, is one of the pods much 

 enlarged ; and we call particular attention 

 to the lateral fibres which are escaping from 

 crevices or fissures on each side of the pod. 

 We could have given other illustrations on 

 this point, showing the gradual opening of the 



pod, and the expansion of the fibres therein 

 contained. Fig. 26, exhibits the ultimate 

 character of the pod when it has burst, and 

 suffered the formation within fully to expand 

 itself. In this state it still retains the bright 

 orange tint. Fig. 31, presents a faithful de- 

 lineation of the feather when all the pods have 

 opened. The three tufts which terminate 

 each division are worthy of regard ; and the 

 beautiful regularity of the whole must excite 

 admiration. It will be noticed that in under- 

 going this wonderful alteration of form, the 

 feather loses much of the fine downy filaments 

 observable in fig. 35. We should likewise 

 remark, that the perfect developement of the 

 feather is in some degree dependent on the 

 position it occupies on the body of the bird ; 

 for we observed several specimens in which the 

 pods gave no sign of opening, though the fea- 

 thers were as mature in other respects as those 

 which were on the point of full expansion. 

 Fig. 36, is one of the finest fibres of fig. 35, 

 magnified 300 times in diameter. In passing 

 from this brief notice of feathers, we would 

 earnestly recommend the admirer of natural 

 beauty, (if he should be a person with sense 

 sufficient not to despise small things^) to amuse 

 his leisure hours by attentively examining the 

 structure of the various plumage that adorns 

 the feathered race. 



We proceed to remark upon the scales and 

 perspiratory pores of the human skin. The 

 scarf-skin of the human body is covered in all 

 parts with rows of exceedingly minute scales, 

 disposed three deep, that is, the first line of 

 scales is in a good degree covered by the se- 

 cond, and the second by the third. The white- 

 ness of the exterior skin is probably owing to 

 this triplication of the scales, since on the lips, 

 where they scarcely overlay each other at all, 

 the minute blood vessels shine distinctly. 

 Owing to the constant friction of the hands 

 and feet, and their becoming callous by con- 

 tinued use, it is not easy to procure good spe- 

 cimens of the scales from these members; 

 but from any of the unexposed parts of the 

 body they are readily obtained, by scraping 

 the skin with the back of a penknife. To the 

 naked eye they appear a mass of indistin- 

 guishable white-dust; but if they be suspend- 

 ed in a drop of water, which causes them to 

 separate, their true form is very pleasingly 

 developed. Their figure resembles the upper 

 half of a spear's head. To obtain a microsco- 

 pic view of the arrangement of the scales, cut 

 from between the fingers with a very sharp 

 penknife, an extremely thin piece of the skin 

 and submit it to a powerful magnifier. The 

 shortest diameter of these scales does not ex- 

 ceed 1- 1 500th of an inch; and their number 

 on a square inch of the human body is not 

 less than one million. 



