1868.] PARKES — RESPIRATION OF INSECTS. 425 



has been described by writers on this subject. But very few, I 

 believe, until lately, have been able to show, by actual demons- 

 tration, to what an almost infinite extent these wonderful air 

 channels divide and sub-divide, and how they spread over and 

 penetrate, almost every membrane and fibre of an insect's body. 

 The principle published accounts of the Respiratory System of 

 insects, have been descriptive chiefly of the larger species of 

 lepidopterous caterpillars ; also of colcoptera, neuroptera and 

 diptera. Preparations of these are of course more easily made 

 and displayed, than the demonstration of the same system in the 

 smaller tribes. As the microscope, however, has gradually 

 been improved, and as microscopic manipulation has also kept 

 honorable pace in the same onward march, so have the more 

 minute marvels of this wondrous material world been gradually 

 unfolded ; and a restless and iusatiate craving has been awakened 

 in the minds of physical philosophers, which has prompted them 

 to see and to touch, not only the most minute organs, of the most 

 minute organism, but even the very molecules of which those 

 natural substances are composed. The great cry of the 

 physiological microscopist now is, More magnifying power — 

 more light. Well, suppose he could obtain both, what would he 

 then want ? Why, most assuredly — I verily believe — something 

 which he does not now possess : more mental power ; and a far 

 more steady and delicate touch, to enable him to handle and 

 separate such infinitesimal forms of matters. And even then, he 

 would still " see through a glass darkly," for he would certainly 

 never touch that invisible essence, which gives vitality to the 

 visible form ! But this is a digression — for my purpose, in this 

 paper, has been, not to speak of what is impossible and unattain- 

 able, but to show what marvellous results have been attained by 

 patient microscopic research, and by persevering practical mani- 

 pulation. As an illustration of this, I have had prepared for 

 examination, not only the larger tracheal system, dissected from 

 the body of a large caterpillar, but the same system of respiratory 

 tubes taken from the body of a human flea. In another slide 

 containing a specimen of Pediculus, the body of the creature has 

 been rendered transparent, and so mounted, as to show the entire 

 respiratory system in situ. Preparations will also accompany 

 this paper, showing the minute ramifications of air vessels over 

 the stomach of the house fly, and of the honey bee, also over the 

 nerve ganglia of a caterpillar. In another slide containing the 



