46 



PLATE XXIV. 



THE FivOGr — contimied. 

 CoMPAKATivE Histology of Frog ani> Man — continued. 

 Fig. 1. Transveuse Section of Feog's Femuk- 



Perios'teum (Gr. peri, around ; osteon, a bone), the investing sheatli of connective tissue. 

 Osteoblast layer (Gr. blastos, a germ), connective-tissue corpuscles arranged in a layer. 

 Bone-cells derived from osteoblasts. 

 Concentric lamellse of bony substance. 

 Figs. 2, 3, 4. Teansverse and Longitudinal Sections of hard compact Tissue of Human Humerus - 

 Haversian canak for blood-vessels to run through, seen branching in fig. 3. 

 Concentric lamellae of bone round each Haversian canal. 

 Lacunaj (L. hollows), oval spaces containing bone-cells (fig. 4). 



Caualiculi (L. little canals), very minute tubes connecting the lacunae with one another. 

 Figs. 5, 6, 7. Muscular Tissue — 



Fig. 5. a, h. Striated or Striped Muscle of Frog taken from thigh — 



( Sarcolemma (Gr. sarx, flesh ; Imima, a sheath), the enveloping structureless 

 ) sheath (not shown). 



MuscuLAK Fibre S Yih^msi, the fibrils composing the fibre. 

 V Nuclei, brought out by acetic acid. 

 Fig. 6. Striped Human Muscle. 



Fibre dividing longitudinally into fibrillas and transversely into disks. 

 Fig. 7. Siiooth or unstriped Musculae Fibres from Humaii Arteries — 

 Individual fibre-cells with elongated nucleus. 

 Figs. 8, 9. Nervous Tissue- 

 Fig. 8 a, b. Nerve-fibres — 



C Primitive sheath, the investing structureless membrane. 

 Nerve-fibre . J Medullary sheath or white substance of Schwann. 



' Axis-cylinder, the central part, fibrillated at origin and termination. 

 Fig. 9. Nerve-cells — 



Granular protoplasm, nucleus and nucleolus. 



Processes or poles sometimes branched and continuous with axis-cylinders of nerve-fibres. 

 Fig. 10. Liver — 



Hepatic or liver cells with nuclei. 



Blood-capillaries in section, from the blood of which the cells secrete or strain off the bile. 

 Bile-capillaries, minute passages shown as swellings between the cells. 

 Fig. 11. Epidermis of Frog, surface view. 

 Fig. 12. Vertical Section of Skin of Frog — 



Epidermis . . . Cells flattened and hardened towards the surface, plump and soft deeper 

 down where produced. 

 f Connective tissue, both varieties (PL XXIII. fig. 6). 

 Dermis or true ) Pigment-ceUs = connective-tissue corpuscles containing pigment. 



Skin ) Cutaneous glands, flask-shaped, lined by epidermis, and opening on the 



V surface. 



Fig. 1 3. Nervous and Connective Elements of Retina of Frog — 



/■ Connective tissue holding the nervous elements together, and extending Iroui 

 \ external limitinfc membrane at the base of the rods and cones to internal 



Connective 



~J limiting membrane in contact with vitreous humour. 



Fibres of Miiller, probably connecting the two limiting membranes. 

 Nervous . . . Rod and cone layer projecting beyond connective tissue, and embedded in 

 choroid. 

 Fig. 1-i. Epithelium prom Nasal Chamber — 



Epithelial cells, columnar, with outer ends broad and inner ends attenuated and branched. 

 Olfactory cells, between epithelial cells, with fine hairs (Frog) or small rods (Man) on outer fine 

 process, and inner probably coming into connection with olfactory nerve, hence the name. 



