March 1, 1869.] 



HARDWICKE'S SCIENCE-GOSSIP. 



51 



analogues the spiral vessels of the vegetable 

 kingdom ; the latter are easily extracted from the 

 young shoots of asparagus, or from the leaves of the 

 hyacinth. The spring-like coil ensures a free open 

 passage for the air which rushes in by the spiracular 

 orifices, expiration being effected by the contraction 



Fig, 41. Trachea; of Geophilus subterraneus, x 140. 



of these elastic channels, by which the effete air is 

 forcibly expelled through the openings by which it 

 originally entered. 



The main tracheal pass down the axes of the blood- 

 channels, floating in the vital fluid, which they 

 revivify with the oxygen which they thus carry to 



and through the life-stream. We are told that the 

 air-pipe does not terminate where the wiry-looking 

 spiral comes to an end ; the latter dwindles away 

 imperceptibly to nothing, but the trachea from 

 thence becomes membranous, and, dividing into 

 innumerable branches, which bear to the main 

 trunks the same rektion that the capillaries bear to 

 the arteries, penetrates the substance of the muscles, 

 inconceivably fine branches having been traced 

 accompanying the nerves, while the ultimate 

 plexiform extremes of the system aerate imme- 

 diately the solids. "In all the transparent struc- 

 tures of insects every observer may prove for 

 himself that the blood-currents travel in the same 

 passages as the tracheal, but this is only the case 

 with the primary and secondary branches, never in 

 the capillary tracheal ; the blood corpuscles of the 

 myriapod exceed by several times in diameter that 

 of the extreme capillary membranous tracheal ; it is 

 perfectly marvellous to what inconceivable minute- 

 ness the air-current is reduced in travelling along 

 these tubes." What a simple and efficient plan, 

 what an economy of space is this arrangement of 

 tube within tube, for aerating the blood in a class of 

 lowly creeping things of earth that do not attain to 

 the dignity of lungs ! There is a saving of time too, 

 for the blood is made arterial while on its journey, 

 and thus travels direct (without the delay of passing 

 off to special pulmonary organs) to the performance 

 of its functions, removing, replacing, renewing, 

 sustaining, building up, absorbing. Having 

 accomplished these, and become as it were venous, 

 it passes into the intervisceral spaces, and there, 

 receiving an increment of fresh globules, the products 

 of digestion, completes its circuit by returning 

 through distinct valvular openings into the dorsal 

 vessel from which it was first distributed. " Among 

 the Chilognatha" says Siebold, "the hdidcewce notice- 

 able for the very simple character of their trachean 

 apparatus ; their air-canals neither ramify nor 

 anastomose. With the Glonicriua the tracheal are 

 branched, but do not anastomose ; but those of the 

 Chilopoda are very ramose, and their large trunks 

 intercommunicate at their origin by longitudinal 

 and transverse anastomoses, so that each stigma can 

 introduce air into the entire trachean system." It 

 was chiefly with the view of drawing attention to 

 this last-mentioned fact (a most striking evidence of 

 design) — to this remarkable, example of the exquisite 

 adaptation of the creature's construction to the 

 condition of existence ordained for it by the Creator— 

 that I began this bit of simple gossip about Geophi- 

 lus. In his subterranean career he constantly meets 

 with accidents which link him up in sympathetic 

 association with Brunei and Stephenson, and the 

 Bedouin of the desert. He never bored a practicable 

 highway beneath the bed of Isis, nor made firm the 

 foundations of an iron road across the quaking 

 surface of Chat Moss ; neither has he braved the 



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