46 

 PLATE XXIV. 



THE FROG" continued. 

 COMPARATIVE HISTOLOGY OF FROG AND MAN continued. 

 FIG. 1. TRANSVERSE SECTION OF FROG'S FKMUR 



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

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

 Bone-cells derived from osteoblasts. 

 Concentric lamellae of bony substance. 



FIGS. 2, 3, 4. TRANSVERSE AND LONGITUDINAL SECTIONS OF HARD COMPACT TISSUE OF HUMAN HUMERUS - 

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

 Concentric lamellae of bone round each Haversian canal. 

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



Canaliculi (L. little canals), very minnte tubes connecting the lacunas with one another. 

 FIGS. 5, 6, 7. MUSCULAR TISSUE 



FIG. 5. a, b. STRIATED OR STRIPED MUSCLE OF FROG taken from thigh 



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



sheath (not shown). 

 MUSCULAR FIBRE "S ., .,, ., ,,, ., . ., ,,, 



J FibriUse, the fibrils composing the fibre. 



V Nuclei, brought out by acetic acid. 

 FIG. 6. STRIPED HUMAN MUSCLE. 



Fibre dividing longitudinally into fibrilke and transversely into disks. 

 FIG. 7. SMOOTH OR UNSTRIPED MUSCULAR FIBRES FROM HUMAN ARTERIES 



Individual fibre-cells with elongated nucleus. 

 FIGS. 8, 9. NERVOUS TISSUE- 

 FIG. 8 a, b. NERVE-FIBRES 



( 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. 



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

 DERMIS OR TRUE \ Pigment-cells = connective-tissue corpuscles containing pigment. 



SKIN ^ Cutaneous glands, flask-shaped, lined by epidermis, and opening on the 



V surface. 

 FIG. 13. NERVOUS AND CONNECTIVE ELEMENTS OF RETINA OF FROG 



(Connective tissue holding the nervous elements together, and extending from 

 external limiting membrane at the base of the rods and cones to internal 



^ limiting membrane in contact with vitreous humour. 



u 



Fibres of Miiller, probably connecting the two limiting membranes. 

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



choroid. 

 FIG. 14. EPITHELIUM FROM 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. 



