Fig. 39. VILTW OF THE BLOOD-VESSELS AND OTHER PARTS IN A PORTION OF THE UPPER 

 SURFACE OF THE TONGUE OF A FROG, THE REAL MAGNITUDE OF THE SURFACE 

 DELINEATED BEING A CIRCLE THE 120TH OF AN INCH IN DIAMETER. DAGUERREO- 

 TYPED BY MESSRS. DONNfi AND FOUCAULT. 



MICROSCOPIC DRAWING & ENGRAVING. 



CHAPTEE II. 



25. Natural tests not invariable. 26. Natural tests imperfect standards. 

 27. Nobert's test-plates. 28. The degree of closeness of their lines. 

 29. Their use. 30. Apparent error respecting them. 31. Fro- 

 nient's microscopic engraving. 32. Method of executing it. 33. 

 Various methods of microscopic drawing. 34. Drawings by squares. 

 35. Dr. Gforing's drawings. 36. Structure and metamorphosis of 

 insects. 37. The day-fly. 38. The larva of this insect. 39. Its 

 organs of respiration. 40. Its general structure. 41. Its mobility. 

 42. State of chrysalis. 43. The perfect insect. 44. The production 

 and deposition of its eggs, and its death. 45. Death may be delayed 

 by postponing the laying of the eggs. 46. They take no food. 47. 

 Their countless numbers ; their bodies used as manure. 



LARDNER'S MUSEUM OF '"CIENCE. p 65 



No. 69. 



