LETTER XXXIX. 



INTERNAL ANATOMY AND PHYSIOLOGY 

 OF INSECTS, CONTINUED. 



CI RCULATION. 



VvE learn from the highest authority, that the blood is 

 the life of the animal a : every object of creation, there- 

 fore, that is gifted with animal life, we may conclude, in 

 some sense, has blood, which in this large sense may be 

 defined Thejluid that visits and nourishes every part 

 of a living body b . But the GREAT AUTHOR of nature 

 has varied the machinery by which this nutritive fluid is 

 formed and distributed, gradually proceeding from the 

 most simple to the most complex structure ; in which he 

 seems to have seen it fit to invert the process observable 

 in the systems of sensation and respiration, where the 

 ascent is from the most complex^ to the most simple struc- 

 ture. In the lowest members of the animal creation, 

 the blood seems the portion they imbibe of the fluid me- 

 dium in which they reside, which when chylified, distri- 

 butes new molecules to all parts of their frame c . In 

 others, as in insects, it is formed by the chyle that tran- 



a Genes, ix. 4. b N. Diet. d'Hist. Nat. xxx. 130. 



e Cuv. Anat. Comp. iv. 167. 

 VOL. IV. G 



