[PLATE XVIII.—Page 558].
SHELLS OF MOLLUSCA.
Fig. 1. Transverse section of spine of Echinus—2. Another section of Echinus, showing reticulated structure, the calcareous portion dissolved out by acid—3. Horizontal section of shell of Haliotis splendens, showing stellate pigment—4. Shell of crab with granules in articular layer—5. Another section of same shell, showing hexagonal structure—6. Horizontal section of coach-spring shell, Terebratulata rubicunda, showing radiating perforations—7. Transverse section of shell of the Pinna ingens—8. Crystals of carbonate of lime, from oyster shell.
[PLATE XIX.—Page 636].
VERTEBRATA.
Fig. 1. a. Spheroidal epithelium cells, filled with central nuclei and granular matter; b. mucous membrane of stomach, showing cells, with open mouths of tubes at the bottom of each, magnified 50 diameters—2. a. Diagram of a portion of the involuted mucous membrane, showing continuation of its elements in the follicles and villi, with a nerve entering the submucous tissue. The upper surface of one villus is covered with cylindrical epithelium; the other denuded, and with dark line of basement membrane running around it; b. epithelium cells, separated and magnified 200 diameters, a central nucleus, with a nucleolus, seen in centre; c. pavement epithelium cells, from the mucous membrane of bronchial or air tubes with nuclei, and nucleoli in some; d. vibratile or ciliated epithelium, nuclei visible, and cilia at the upper free surface, magnified 200 diameters—3. a. is one of the tubular follicles from a pig’s stomach, cut obliquely to display upper part of cavity, and the cylindrical epithelium forming its walls, a few cells detached; b. shows a section of a lymphatic, with capillary blood-vessels, distributed beneath the mucous surfaces—4. Cells of adipose tissue, or fat, magnified 100 diameters—5. a single fat-cell separated, and magnified 250 diameters—6. A capillary of blood-vessels distributed through tissue—7. Section of the Tendo-Achillis as it joins the cartilage, showing stellate cells of tendon, seen to be gradually coalescing to form round or oval cells of cartilage—8. A vertical section of cartilage, with clusters of cells arranged in columns previous to their conversion into bone—9. A small transverse section of the same, showing the gradual change of the cartilage cells at a. into the true bone cells, lacunæ, at b. with characteristic canaliculi—10. A stellate nerve corpuscle, with tubular processes issuing forth, at a. filled with corpuscles containing black pigment, above which is a corpuscle the nucleus of which is seen to have nucleoli; at b. a corpuscle enclosed within sheath, and filled with granular matter taken from the root of a spinal nerve—11. The continuity of muscle, the upper portion, with connective tissue of the lower portion, from the tongue of a lamb—12. Branched muscle, ending in stellate connective cells, from the upper lip of the rat—13. Choroidal black pigment-cells from the human eye.
[PLATE XX.—Page 658].
BONE STRUCTURE.
Figs. 1. and 2. Transverse section of the human clavicle (collar bone), showing Haversian canals, concentric laminæ, and concentric arrangement of bone cells—3. Transverse section of the femur of an ostrich—4. Transverse section of humerus (fore-arm) bone of a turtle, Chelonia mydas—5. Horizontal section of the lower jaw-bone of a conger eel, in which no Haversian canals are present—6. A portion of the cranium of a siren, Siren lacertina—7. Portion of bone taken from the shaft of humerus of a Pterodactyle, showing elongated bone-cells characteristic of the order Reptilia—8. Horizontal section of a scale, or flattened spine, from the skin of a Trygon (sting-ray), showing large Haversian canals, numerous wavy parallel tubes, also bone-cells with canaliculi communicating as in dentine.