ON MICROSCOPIC DISCOVERY. 



603 



succeeded in examining transverse sections,) 

 nearly the same vegetable characteristics. In 

 general, however, the cups are more readily 

 distinguished in hairs than in the nails, or 

 porcupine's quills, and other objects of this 

 class ; there is also a much greater variety of 

 structure in the former than in the latter. 

 Plate 34, figs. I to 7, exhibit some interesting 

 varieties of hairs, of which we shall speak in 

 order. We give no illustration of the human 

 hair, because in the adult its character is so 

 much defaced by friction, that it exhibits, 

 even under a deep power, little more than the 

 appearance of a polished cylinder. In the 

 hair of an infant newly born, the serratures 

 on the sides, or more properly, the cup shaped 

 processes, are readily distinguished ; we had 

 not, however, when engaged on our drawings, 

 an opportunity of procuring a specimen. Hairs 

 may be described generally as cylindrical 

 bodies, composed of a vast number of minute 

 fibres, with cellular cavities interposed ; some 

 have spiral lines running up the interior ; and 

 from observation of a few varieties, it may be 

 inferred that all are furnished with an appa- 

 ratus resembling the stomata in the leaves of 

 vegetables. We proceed at once to describe 

 the figures before referred to. 



Fig. 1. The hair of the Dermestes. This 

 insect belongs to the order coleoptera, and is 

 remarkable for the beautifully formed hair 

 which covers it in the larva state. There is 

 a variety in the structure ; some of the hairs 

 resemble an oat beard, and others exhibit the 

 character shown in our specimen. A more 

 delicate and beautiful object than the spear- 

 shaped hair can scarcely be submitted to the mi- 

 croscope. The lowest power by which it can 

 be seen, is 100 linear ; but to develope its 

 details satisfactorily, a power of 200 linear is 

 requisite, which is the one we have used. 

 This object is considered an excellent test of 

 the defining power of a good microscope. 



Fig. 2. *" The hair of a mouse. The char- 

 acteristics of this subject, when viewed by 

 transmitted light, are dark, transverse stripes, 

 some of which are broken, whilst others extend 

 quite across the hair. On closer and more 

 attentive observation, these appearances are 

 discovered to arise from a kind of spiral spring 

 occupying the tube of the hair, and a number 

 of im perforations on the surface. 



Fig. 3. The hair of a bat. From the re- 

 semblance between the mouse and the bat, it 

 will excite a little surprise to observe the very 

 decisive difference of structure in the hairs of 

 these two animals. That of the latter some- 

 times presents the appearance of a screw, or 

 of a number of small conical cups inserted 

 into each other ; other specimens seem to be 

 formed of two distinct hairs twisted together ; 

 and some exhibit in connection with these pe- 



culiarities, striped markings resembling those 

 on the hair of the mouse. 



Fig. 4. The hair of a bee. This is a very 

 beautiful object, but requires a good defining 

 power to show the structure satisfactorily. 

 The hair itself resembles a jointed bamboo 

 cane ; and from each joint small delicate 

 spines shoot out. The hair terminates in a 

 number of these spikes, one of which is uni- 

 formly longer than the rest. 



Fig. 5. The hair of a. dormouse. This is 

 very similar to the hair of a mouse. The 

 points of difference seem to consist in the 

 regularity of the stripes on that of the dormouse, 

 and its greater delicacy. 



Fig. 6. The hair of a mole. This is a most 

 singular structure. The interior exhibits the 

 remarkable transverse stripes observed in the 

 hair of the mouse and dormouse, and the ex- 

 terior presents a formation somewhat resem- 

 bling that of the bat's hair. 



Fig. 7. The. hair of a caterpillar. We 

 notice a great similarity between this object 

 and the hair of a bee. The tube of the hair 

 is not jointed, however, in the caterpillar, and 

 the lateral spines curve the contrary way. 



These objects are all shown as developed 

 by a doublet linear power of 200. 



The next animal appendage to which we 

 shall allude is the feathers of birds, wherein 

 we notice very distinctly the same degree of 

 analogy to vegetable formations, as is found 

 to exist in the hair, &c. The microscopic in- 

 quirer is frequently called upon to pause and 

 admire the wonderful adaptation of parts in the 

 various structures he examines ; and to note 

 the absolute dependency of the largest forma- 

 tions on the microscopic elements of which 

 they are composed. Let us illustrate this 

 remark in the case of feathers. The feathers 

 of birds unite to form the wing, a locomotive 

 member which must be light, yet at the same 

 time impervious to air ; which must have 

 great freedom of motion, and yet not be liable 

 to permanent disarrangement of its parts. The 

 most superficial observer will have noticed the 

 way in which the feathers are disposed in the 

 wing ; they over-lap each other through their 

 whole length, and this principle of over lap- 

 ping extends to all the divisions and minute 

 subdivisions of the feathers. Another thing 

 also is too obvious to have escaped notice, that 

 the upper side of every feather is convex, and 

 the under side concave, and that the convex 

 side of one feather lies partly within the con- 

 cave side of another. This principle of forma- 

 tion likewise extends to the most minute parts. 

 Then again there is an elastic force exerted in 

 every feather, and in every part of a feather 

 for preserving and restoring the natural ar- 

 rangement. There is, in short, a beautiful 

 display of creative Wisdom in the wing of a 



