Dec. 28, 1883.] 



KNOWLEDGE ♦ 



383 



°n 



|;^jt ^'^ .AN IIAiL&TRATED 



^' MAGAZINE OF SCIENCE 



I PLAINLyiybRBED-EXACTL^DESCRIBFD 



LONDON: FRIDAY, DEC. 28, 1883. 



Contents of No. 113. 



i'leasant Hours with Hie Micro- 

 scope. By H. J. Slack 383 



The Universe of Suns. II. By 



R. A. Proctor 381 



The Chemistry of Cookery. By 



W. M. Williams 383 



Mind in the Infant 388 



Tricycles in 1883. By J. Browning 387 



Astronomical CoUi.iions 388 



Recreation by AVonder 389 



Fiex 



The Burgin Dynamo-Electric Ma- 

 chine (Illua.) 390 



The Vibrato 392 



An Ancient Comet. By W. St, 

 Chad Boscawen 393 



The Possible Suspension of Old 

 Age. By W.V.Dawson 393 



Correspondence : Strange Lake Wave 

 and Sunsets— Tricycles, &c 396 



Our Chess Column 398 



PLEASANT HOURS WITH THE 

 MICROSCOPE. 



By Henry J. Slack, F.G.S., F.R.M.S. 



AUTHORS u.snally Jay all lilame for mistakes to the 

 printer.s, but I will be more geuerous, and confe.ss I 

 may have overlooked, in correcting the proof, that in the 

 second paragraph, p. 316, Nemoptera appears instead of 

 Neuroptera. 



There is a common notion that insects are enormously 

 stroni; for their size, which is true, without the fact neces- 

 sarily leading to the fancy that if larger creatures had pro- 

 pM'tional muscular power, they could jump over steeples, 

 and give mountains a shake. The muscular system of 

 insects is, however, very wonderful and well worth exami- 

 nation. If, for example, the thorax of a wasp or bee is 

 opened, the observer will see a number of yellowish bundles. 

 A slight touch will separate them into fibrils, and, under 

 the microscope with a power of about 300 x , these will be 

 resolvable into Jibrilla', very delicately striated across their 

 length. 



In the human body, and in invertebrates generally, the 

 striated muscles belong to the voluntary .system, and non- 

 striated to most of those organs over which the will has no 

 direct control. >Siebold tells us that the muscular fibres of 

 the iusecta are striated, not only in the voluntary muscle.?, 

 but often also in those of organic life, as in the stomach and 

 intestines. INIuscular fibres from the tliorax of insects do 

 not exhibit the .striation nearly so plainly as tho.se from 

 some other parts. For example, such fibres from the thoi-ax 

 of a wasp require a little care in o[)tical management 

 for their striation to be seen at all, while in fibres from the 

 muscles moving the stinging api)aratus of a hornet, they are 

 obvious with less magnification. The quantity of muscle in 

 Ihe thorax of a four-winged insect is strikingly large. The 

 work to be done is to give due motion to six legs, besides 

 the wings. The latter organs have to move with consider- 

 able ra])iditj' during flight ; but the space they traverse in 

 each vibration is small. Tiie wing movements ai'e j>ro- 

 duced, according to Siebold, by two extensor and several 

 small flexor muscles, which arise from the middle and 

 posterior thoracic segments, and are inserted on a tendinous 

 process at the base of each wing. In insects that use four 



wings equally in the act of flying, the muscles moving in 

 two pairs are equally developed ; but those of the anterior 

 wings of bugs and some other insects whose flight is wholly 

 or chiefly j)erfornied by the hind wings, are smaller in size. 



The wings of dragon-flies, bee.s, and house-flies are strong 

 and firm in proportion to their size, which enables them to 

 oppose a considerable resistance to the air. According to 

 an old observation of Leeuwenhoek, a species of dragon-fly 

 outstript a swallow which tried to catch it in a menagerie 

 200 feet long, but for this rapid flight the muscles are not 

 requiied to make the wings vibrate any great number of 

 times in a second. According to an article by Mr. J. 

 Bi-hop, ir. Tod's " Cyclopedia of Anatomy and Physiology" 

 an ^> lina, causes its wings to vibrate ninety-six times 

 in a second, as a prt-liminary to flying, when the vibrations 

 become slower, but through larger arcs. The force employed 

 as estimated by the weight moved through a certain space 

 in a given time, does not appear so striking as when only 

 the rapidity of the flight is considered. 



If an insect is caught in the fingers its struggles to escape 

 give tlie notion that its strength is excessive for its dimen- 

 sions, and experiments to ascertain what weights insects 

 can pull up inclined planes have been held to confirm the 

 opinion. This, however, is controverted by M. Delbeuf, 

 in a paper called " Nains et Grants (" Dwarfs and Giants") 

 which appeared in the Revue Scientijiqne, Jan. 27, 1883. 

 He cites M. F. Plateau's statements, derived from careful 

 experiments, to the effect — " 1. That in the matter of 

 flight, insects in relation to their weight possess enormous 

 strength compai'ed with vertebrates ; 2. That in the same 

 group of in.sect? the strength of difterent species varies 

 inversely as their weights, or, in other words, the smallest 

 are the strongest. If, says M. Delbeuf, the strength of a 

 horse weighing GOO kilogiammes, as measured by Regnier's 

 dynamometer, equalled -tOO kilogrammes, and if a cock- 

 chafer weighing a sixth of a gram me could exert a force of 

 sixty-six times its weight, it would be proportionably one 

 hundred times the stronger, and 40,000 cockchafers would 

 be equal to a large horse. " Must we," he exclaims 

 " resign ourselves to be a hundred times less vigorous tlian 

 a cockchafer, and two hundred times less strong than a 

 small beetle that lives in dung ? " He replies in the 

 negative, and contends that the element of time is omitted 

 in these calculations. " Suppose," he says, " a horse har- 

 nessed to a burden equal to half his own weight, and a 

 chafer to another one fifty times its weight, if the horse 

 raised his burden one metre in a second, and the chafer 

 required one hundred seconds to raise his to the same 

 height, the two efforts would be proportionably the same." 

 After giving many illustrations, M. Delbeuf concludes 

 that all animals are about on a level, and that muscular 

 fibre has the same properties, whether in a vertebrate, arti- 

 culate, or moUusk. 



To return to our insects, it is evident on inspection that 

 their thorax contains a large quantity of muscular fibre in 

 ])roportion to its capacity. There is no waste of space ; the 

 fibre is closely packed, and free from fat or other inert 

 material, and the whole body of an insect is usually very 

 mus^cular in proportion to its size and weight. 



The muscular fibres of insects should be compared with 

 those of other creatures. Any kind of meat well boiled 

 is likely to show them jilainly. A very small piece should 

 lie taken, teased out with a needle on a slide in a drop of 

 water, and covered with a thin glass, and examine 1 with a 

 I or higher power. 



Amongst the aspects presented by striated fibrils under 

 high magnification is one of a series of light squares, con- 

 taining smaller and darker squares. These must be regarded 

 as optical appearances, not positive exhibitions of structure. 



