By putting various substances, such as spirit or salt, upon the foot, the rapidity of the circulation at the spot can be greatly increased or reduced at will, or even stopped altogether for a while, and the phenomenon of inflammation and its gradual natural cure be beautifully illustrated. The numerous black spots upon the surface are pigment-cells.
The tails of young fish also afford excellent objects under the microscope, as the circulation can be seen nearly as well as in the frog’s foot. The gills of tadpoles can also be arranged upon the stage with a little care, and the same organs in the young of the common newt will also exhibit the circulation in a favourable manner. The frog, however, is perhaps the best, as it can be arranged on the “frog-plate” without difficulty, and the creature may be kept for months by placing it in a cool, damp spot, and feeding it with flies, little slugs, and similar creatures.
CHAPTER VIII
Pond-Life—Apparatus and Instructions for Collecting Objects—Methods of Examination—Sponge—Infusoria.
Of all departments of microscopic research the most fascinating and the most popular is that which deals with what is known by the generic name of “pond-life.” The minute forms of the animal creation included in this term are of such exquisite beauty, and allow the processes of their life-history to be followed with such facility, from the cradle (when they have one) to the grave (which is very often the body of another, larger, organism), that there is none which has attracted more observers. Indeed, the first application of the microscope, by Leeuwenhoek, early in the seventeenth century, was to the observation of these forms of life.
X.
| FIG. | |||
| 1. | Skin, Frog | 18. | Do. Wild Duck |
| 2. | Blood, Human | 19. | Circulation of blood, Frog’s foot |
| 3. | Do. Pigeon | 20. | Feather, Sparrow |
| 4. | Do. Proteus | 21. | Do. Cock’s tail |
| 5. | Do. Tortoise | 22. | Fibre, crystalline lens of fish |
| 6. | Do. Frog | 23. | Nerve |
| 7. | Do. Fish | 24. | Muscle, Meat |
| 8. | Human nail | 25. | Tooth, transverse section |
| 9. | Bone, Human | 26. | Do. Longitudinal section |
| 10. | White fibrous tissue | 27. | Sweat duct |
| 11. | Epithelial cells from tongue | 28. | Eye of Haddock |
| 12. | Feather, Peacock | 29. | Myliobates, palate |
| 13. | Spine, Hedgehog, transverse section | 30. | Gristle, Pig |
| 14. | Pax-wax | 31. | Pigment, Human eye |
| 15. | Epithelial cells from nose | 32. | Do. Wing of Bat |
| 16. | Bone, Ostrich | 33. | Do. Shell of Prawn |
| 17. | Feather, Shaft of Canary’s |