70 



UNDULATORY FORCES. LIG HT. 



[MICROSCOPIC OBJECTS. 



with insects. These should be carefully collected by 

 dipping with a basin from the pond; and must then 

 transferred to a tall glass vessel, filled with water. lnt< 

 this a few plants should ln> introduced ; and those growing 

 beneath the surfaco of the pond front whieh the insects 

 hay.o been withdrawn, will perhaps be the best. A 

 littlo of the earth should bo removed with them, am' 

 the plants will thus thrive in tho vessel; and by their 

 action on tho water they will tend to keep it fresh, anil 

 fit for animal existence. Indeed, such an arrangement 

 forms a small aquarium. By similar means we hu\x 

 been able to keep a good stock of insects throughout tin 

 year ; and have often surprised our microscopical friends 

 by exliiMtini; many curious and interesting little crea- 

 tures in tho depth of winter, by aid of the oxy-hydrogcn 

 microscope. Fresh water should bo occasionally added ; 

 nnd the temperature should never be allowed to go 

 below 00 Fan. In such a collection the student will 

 bo surprised to find an immense variety of objects. 

 \\ shall speak of many of these under tho head of 

 : ral History ; to which, or to any work of a similar 

 kind, we must for the present refer our readers. 



The unlimited number of land insects, places at the 

 disposal of the microscopist a most interesting field for 

 investigation. As it would be impossible for us to enu- 

 merate or classify such objects, we shall content ourselves 

 by pointing out only those parts of most insects which 

 require special notice. We must first say a few words 

 as to catching, killing, and mounting. 



Generally speaking, insects of the moth kind are best 

 caught about dusk ; and this should be done by means 

 of a fine gauze net, similar to one already described and 

 illustrated;* the sack, however, being larger, and of 

 lighter materials. By this method, the wings, antonnro, 

 <!zo., are uninjured. With respect to killing insects, the 

 best plan we know of combines the advantages of pro- 

 ducing instant death, and retaining the colours, <fcc., quite 

 uninjured which is by means of carbonic acid. In 

 endeavouring to simplify the process of making tho 

 gas, we suggest the following plan : Place an ale- 

 glass in a confectioner's show-glass ; and into the for- 

 mer put a teaspoonful of chalk or whiting. On this 

 pour some vinegar and water, or a littlo hydrochloric 

 acid, diluted with five times its bulk of cold water. 

 ( >n the top of the ale glass place a small card, so as to 

 eritirely cover it. The carbonic acid will gradually es- 

 cape, and, being heavy, will flow out of the ale-glass, 

 and till the larger vessel. Any insect dropped into the 

 latter will instantly fall down dead to the bottom, with 

 wings extended ; and, in fact, will preserve in death every 

 external appearance of life. The card of course prevents 

 the insect from falling into the mixture ; and none of 

 this should be allowed to flow into the outer vessel. 

 Fig. 54. Fig. 54 represents this simple 



and effective arrangement. 



The insect, if small, may 

 then be placed between two 

 slips of window-glass; but 

 this should not be done until 

 all the moisture has been 

 dried out of the body. This 

 is best done by leaving tho 

 insect for some days in tho 

 open air, and in sunlight. 

 The mode of mount n 

 the actual size of the glass 



a, the outer *!.< vo^l ; , the I>late, aiv already described. t 

 alr-nlaM, com .iniiriu \\n- mixture Considerable delicacy 13 re- 

 producing carbonic acid ga.. quired in separating tho 

 various parts of insects, such as the antenn.-u, eyes, wings, 

 legs, stings, <bc. ; but such can only bo gained by long 

 practice, and great care. Instruments, such as fi 

 and small lancets, are often supplied with compound mi- 

 croscopes for such purposes ; and whilst attempting those 

 operations, a magnifying glass should be used, which will 

 enable the operator to proceed with greater certainty. 

 When the part has been removed, it should be placed on 

 the centre of a piece-glass, half an inch wide and three 



See ante, p. 63, Fig. 52. \ Ant', l>. 68, Fig. 53. 



iii. -lies loir.;. :,:i.l on it a drop of Canada balsam may bo 

 poured. This preserves the object from injury by 

 shifting, A-c. : the arrangement is completed by placing 

 another slip of glass over the balsam when dry, and the 

 edges of tho two slips may then be pasted together, as 

 already mentioned. In a hintilar manner, the hair, down, 

 of insects, birds, or animals; and the scales, etc., of 

 fishes, may be preserved from injury, and placed in a fit 

 condition for microscopic purposes. 



va or eggs of insects '.illy found in cre- 



vices or slits iu wood, <tc. ; and from their exti 

 minuteness they actually require, in many instances, a 

 microscope to discover them. Dust and dirt, so called 

 (which, however, lias been defined as "matter in the 

 wrong place"), are often prolilic with these objects. 

 Indeed, we would venture to suggest the use of the 

 microscope to many housewives, who might thus dis- 

 cover tho cause of the appearance, of "such swarms" 

 of certain insects; and being so forewarned, might take 

 the necessary steps for preventing their subsequent pre- 

 sence in a lively and predatory state of existence. 

 So extremely small, indeed, are some of these 

 that they have not been seen by aid of even tin \ 

 powerful microscopes. Hence has arisen the alntd 

 theory of "spontaneous generation," an idea as tli 

 ditable to the reasoning powers of a man, as it is an 

 evidence of the crudeuess of his imagination. \Ve nerd 

 but further say here, on this subject, that if any creature 

 could create itself, a Creator would be unnecessary ; for, 

 .is the most minute living thing that has yet been ex- 

 amined, has organs which, iu their construction, func- 

 tions, and use, are analogous with those of the la. 

 size of animals, it follows that the creative power should 

 exist in every being, small or great ; the result being only 

 modified by the individual ability or strength of self- 

 creation in each species an argument too ridiculous to 

 require refutation. Moreover, the advocates of the 

 theory must admit, that inanimate matter must also have 

 been self-creative, to be consistent in all their proposi- 

 tions: of this idea, however, they decline to take the 

 responsibility ; and thus they attempt to build an edifice, 

 but forget first to lay its foundation. 



An interesting class of objects is found in insects which 

 are bred, grow, and feed in various animal substances. 

 Amongst these we may mention the mites in cheese, the 

 maggot, and parasitic creatures, such as the louse, the 

 tick, itc. These are generally regarded with a degree of 

 disgust, which, however, should not be shared in by any 

 student of science. Duties of the most offensive kind 

 are necessarily undertaken by those experienced in scien- 

 tific pursuits, for the purposes of jurisprudence, which 

 require the exercise of great nerve in their pursuit. The 

 student, however, is not called to these, and may not 

 object to examine any of the productions of nature be- 

 cause, under certain circumstances, these may prove 

 offending bearing hi mind, that whatever the Deity has 

 made is worthy of man's investigation. 



Directing our attention to the organs of animals, we 

 may mention, that a most instructive branch of inquiry 

 is found in comparative physiology and anatomy. Com- 

 mencing with tho heart, we may remark, that that organ 

 has its representative in every kind of breathing crea- 

 tures. The circulation of the blood, the nervous and 

 muscular systems, the perspiratory ducts, the skin, bone, 

 fibre, hair, down, feathers, are mostly found in actual 

 existence, or substituted in each order ; and an intense 

 interest is created in tho search for these in different 

 species, or the discovery of their modifications. Under 

 the description of the oxy-hydi"i'< n mimiM-upo and its 

 uses, we have made special mention of the nature of 

 blood globules, and their characteristic differences in ani- 

 mals ; a subject of importance in a philosopliical and 

 even legal point of view. 



We have thus indicated some of the interesting objects 

 io be found iu various departments of the animal king- 

 dom, and must leave our readers to complete that which 

 we cannot further extend without encroaching on tho 

 imits of our plan. 

 A very interesting field is o]>cned out in the vegetable 



