Fig. 4. For the admission of air there are only two openings,both situated near the tail, which it brings to the surfaceof the water whenever it is necessary to take a fresh sup-ply. Fig. 6 is a magnified portion of the trachea, to 56 MICROSCOPIC OBJECTS. exhibit the spiral nature of its structure.… … Fig. 5. Fig. 6. Fig. 7. structure admh-ably illustrates the interference of light.For this purpose the shde containing the tracheae shouldbe held close before the eye, when looking through itat a lighted candle about a yard distant; the colouredimages will then be seen on each side of the real…
Microscopy
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![An illustration from Medical zoology and mineralogy. Or, Illustrations and descriptions of the animals and minerals employed in medicine, and of the preparations derived from them; including also an account of animal and mineral poisons, with figures coloured from nature / [John Stephenson]. (1832)](https://img.insideoutlibrary.com/img/200/wellcome-wellcome_b22010932-205-1.webp)
