66 



THE POPULAR EDUCATOR. 



feeding bird. The swallow, which plunges with such reckless 

 impulse through the air, will nevertheless seize a small insect 

 as it dashes along with almost unerring certainty. Usually the 

 prey is so small, that the wonderful powers of the bird dis- 

 played in the chase cannot be observed ; but sometimes, when 

 the insect has large wings, this dexterity may be seen. 



The writer has seen a swallow seize, while in headlong flight, 

 Jie beautiful, scarce swallow-tail butterfly, and shear out its 

 sapid body from between the wide wings, and let them float 

 severally down ; and then, not satisfied with a feast so little 

 proportioned to the splendour in which it was dished up, glance 

 round and seize again the several pieces before they had time 

 to reach the ground. How, then, is a long sight and a keen 

 short sight to be obtained from the same eye ? This is done 

 mainly by the aid of the bony plates already described. These 

 are so disposed that the edge of one is capable of sliding over 

 the edge of its next neighbour, so that when the fibres of the 

 muscle which unites them contract they compress the eye all 

 round and make it more tubular, while the humours of the eye, 

 thus subjected to pressure, cause the cornea to protrude more, 

 and also the retina to be removed further from the lens. These 

 motions aro, in addition to the adjustment for distance, found 

 in mammals. 



Intimately connected with this pressure upon and alteration 

 of the dimensions of the humours of the eye, is another pecu- 

 liarity in the eye of a bird. This is a puckered, parse-like 

 membrane, which is attached to the optic nerve, which in this 

 class enters into the eye by a slit-like opening. This membrane 

 is sometimes called a marsupium, from its resemblance to a 

 purse, and sometimes a pecten, from its supposed likeness to a 

 comb. It stretches to the interior of the eye to a different 

 extent in different birds, and is composed of a tangled mass of 

 blood-vessels, mixed with pigment granules. Whether this is 

 simply an erectile organ, which can rapidly contract and enlarge 

 kJuddenly as it is deprived of or injected with blood, or is capable 

 of feeding the vitreous humour with liquid strained by it from 

 the blood, and draining it off again as circumstances require, is 

 not known. 



The eyes of reptiles are so different from one another, ranging 

 in structure between the eye of the bird and that of the fish, 

 that it is better at once +o pass on to a description of an eye 

 adapted to sight in water. 



A fish, living as it does m an atmosphere which is many hun- 

 dred times denser than ah-, and by no means so transparent, 

 must have an eye suited to look at near objects. It must 

 therefore be able to concentrate the rays of light rapidly ; yet 

 it is under this disadvantage, that as it is only when passing 

 from a rare into a dense transparent convex substance that 

 diverging rays are bent towards one another, and the original 

 rays pass through a dense medium, the cornea and aqueous 

 humours can play no part in the bending of the rays towards 

 one another, for they are of about the same density as water. 

 The whole duty of refraction must thus be done by the lens. 

 This is very dense, and of the sheets of which it is made up the 

 inside are denser than the outside, while it is so convex both 

 before and behind as to become a perfect globe. 



Both the consistence and shape of the round lens may be 

 Been by squeezing it out of the eye of a cooked fish, even by 

 those whose taste for comparative anatomy is only stimulated 

 at the dinner-table. 



In connection with this kind of lens we have a shallow eye. 

 In other words, if the cornea, through which light enters, be 

 turned upwards, the back of the eye on which the retina is 

 spread resembles a saucer, and not a cup as it does in animals 

 and birds. 



This is so much the case, that even though the hard capsule 

 is shallower than in brutes, there is still left a large space 

 between this and the choroid, and even this latter has between 

 two of its layers a horse-shoe shaped "gland" composed of 

 blood-vessels, something like the pecten of a bird, though in a 

 different place, and with exactly a converse function. 



The hard outer coat is strengthened and held to its form by 

 a cup-shaped bone or cartilage, which occupies the parts which 

 are left unoccupied by the bird's eye-bones ; because while the 

 latter are used to elongate the eye this maintains a shortened 

 axis. 



The cornea, or window, and the watery fluid behind it being 

 Meless to collect the rays are left, the one flat and the other 



in small quantity, and the result of this is that the fish can see 

 distant objects as well through the air as through the water ; 

 and this is important, because almost all fish are surface fish ; 

 many feed on flies, and most have to be on their guard against 

 aerial foes. The reader, then, need not be surprised when the 

 sun-loving shoals of carp or chub all plunge headlong into the 

 depths when he appears on the river bank. 



As a singular instance of the adaptation of means to ends, 

 it is found that all animals, whether reptiles, birds, or brutes, 

 vhich are amphibious, or which spend much time in the water, 

 have eyes which, though they differ from those of fish, in some 

 things have the same relation of the cornea and lens. Thus 

 the whale and the dolphin (which are but brutes which Have 

 taken to the sea), the cormorant and diver, the frog and the 

 crocodile, have all spherical lenses and flat corneas. 



FibU and frogs have on the outer layer of the choroid a layer 

 of silvery or golden crystals, and this layer, which is continued 

 round till it occupies the front layer of the iris, gives to the 

 toad so metallic and bright an eye as to countenance the legend 

 that it has a jewel in its head. So Shakespeare 



" The toad, ugly and venomous, 

 Wears yet a precious jewel in its head." 



LESSONS IN GERMAN. IV. 



SECTION VIII. INDEFINITE ARTICLE. 



THE indefinite article is less varied than the definite, having for 

 the masculine and nouter nominative but one form, as 



Masculine : e i n 2)iann, a man. Neuter : tin la, a glass. 



DECLENSION OF THE INDEFINITE ARTICLE MASCULINE AND 

 NEUTER WITH NOUNS. 



Masculine. Neuter. 



5)1. (Stu aJiann, a man ; cin Jltnb, a child ; 



65. (5inc8 3)iannc3, of a man ; etneS JUnbeS, of a child ; 



3X GHncm Q)iaiinc,to,forainan; eincm Jtinbt, to, for a child; 



31. (Stnen SDtann, a man ; ein Jltnb, a, child. 



OF THE COMPOUNDING OF NOUNS IN GERMAN. 



1. Nouns are more frequently compounded in German than 

 in English ; and accordingly one word in German often requires 

 for its full translation several in English, as : 



SBirfttiKjgfreiS, sphere of action (action sphere) ; 

 @d?tt>immogel, web-footed bird (swimming fowl) ; 

 5iaftt()icr, beast of burden (burden animal) ; 

 3"gtf)tcr, draught animal ( 2. 7) ; 

 &au8tl)ier, domestic animal (house animal). 



VOCABULARY. 



BESUME OF EXAMPLES. 



!cr SSctf ifl ein SRaufrtfjicr. The wolf is a beast of prey. 



3?cr 3im'mermann ifl ein -anb The carpenter is a mechanic. 



tnerfcr. 

 3)er jammer ifi ein SBerfjeug. 



if, JBin'bcnjort ifl ein 9Jcbet^ctI. 



!Der Sftame 'ctneS 35inge ifl 



2)ingnjort. 

 Da8 JJitrt liefet ben rofj'sater. 



The hammer is a tool (an in- 

 strument). 



The conjunction is a part of 

 speech . 



The name of a thing (substance) 

 is a substantive. 



The child loves the grandfather. 



EXERCISE 9. 



1. >$at ein Oftann, cber ein fltnb bcu Stocf btefeS JreuubeS ? 2. 3)tefcr 

 SDfann I;at ein @d)h>crt eine geinbe?, unb biefcS tftnb Ijat ben @t! cincS 

 SrcunbeS. 3. S3k8 feat bee Sfiqer? 4. @r &at einen > ( >unb unb dr. 



