1868.] PARKES — RESPIRATION OF INSECTS. 419 



however idle or blind man may be in seeking to understand tlie 

 sublime plan ! 



As, however, it is not my purpose in this paper to offer a new 

 designation for these strange and diversified animals, but rather 

 to describe an important and essential peculiarity in the anatomy 

 and physiology of the entire class, (which, by the way, might per- 

 haps forma very scientific groundwork for their classification,) I 

 will now proceed to the discussion of my subject. 



A careful study of the structure and functions of organs, as 

 developed in the lower animals, has long been considered by com- 

 parative physiologists, an important and instructive pursuit. We 

 may thus see functions performed by the simplest possible 

 structural arrangements, and may learn what are the essentials 

 of such organs. Dr. Goadby (the once English but now Ameri- 

 can professor of comparative physiology,) remarks in his beauti- 

 fully illustrated work on this subject, "that in this class (Insecta) 

 the most important problem — the ultimate structure of glands — 

 may be studied with great ease. In the higher animals, these 

 organs are veiled by a parenchyma, which renders investigation 

 difficult ; but in insects we find them already analyzed — existing 

 as simple tubuli, and offering every facility for the most minute 

 examination of them. When the like organisms in man and the 

 higher animals have been successfully treated and reduced to 

 their elemental conditions, lo ! they too, are simple tubes !" Now 

 with regard to the special function of respiration, I think some 

 important truths may be elicited, by a careful study of the very 

 beautiful and elaborate arrangement by which it is effected in 

 the insect race. It will scarcely be needful to observe — even in 

 the most casual way — what an important part is played by this 

 function in the economy of all organized beings. Most animals 

 can exist for a considerable period without food ; although this is 

 an essential condition to the continuance of their life. But if the 

 function of respiration be suspended, even for a very limited 

 period, death is the speedy and inevitable result. Now the 

 necessity for respiration in all animals — whether aquatic, 

 terrestrial or aerial — results from the fact, that a continual decay 

 takes place during every moment of such an animal's existence. 

 Waste and renewal form one of the prominent pecularities of 

 organic life. And one of the peculiar phases of this physiologi- 

 cal law is, that activity and waste bear a definite relation to each 

 other. The more active any organ, or set of organs may be, the 



