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Muscles of the back. Labels: 50, latissimus dorsi; 51, trapezius; 52, deltoid. The muscles of the back are in 5 layers, one beneath another. The two largest and most superficial are the trapezius and the latissimus dorsi.

Muscles of the Human Back

Muscles of the back. Labels: 50, latissimus dorsi; 51, trapezius; 52, deltoid. The muscles of the back…

Diagram illustrating the general arrangement of the cerebrospinal nervous system.

Diagram of the Human Nervous System

Diagram illustrating the general arrangement of the cerebrospinal nervous system.

Diagram showing anatomy of the spinal nerve roots and adjacent parts. Labels: G., gray matter of the spinal cord; W., white matter of the same; D.H., dorsal horn of gray matter; V.H., ventral horn of gray matter; D.R., dorsal root of spinal nerve; Sp.G., spinal ganglion; V.R., ventral root of the spinal nerve; Sp. N., spinal nerve; Rc., communicating branch (ramus communicans); S.G., sympathetic ganglion.

Spinal Nerve Roots

Diagram showing anatomy of the spinal nerve roots and adjacent parts. Labels: G., gray matter of the…

Piece of human hair, highly magnified. Labels: a, cuticle; b, fibrous substance; c, medulla.

Piece of Human Hair

Piece of human hair, highly magnified. Labels: a, cuticle; b, fibrous substance; c, medulla.

Diagrammatic longitudinal section of the trunk and head. Labels: 1,1, the dorsal cavity; a, the spinal portion; b, the cranial enlargement; c, c, the bodies of the vertebrae forming the partition between the dorsal and ventral cavities; 2, 2, the ventral cavity, subdivided into thoracic cavity (d), abdominal cavity (e), and pelvic cavity (f); g, the nasal cavity; h, the mouth, or buccal cavity. The alimentary canal (al) is represented running through the whole length of the ventral cavity.

Trunk and Head of Human Body

Diagrammatic longitudinal section of the trunk and head. Labels: 1,1, the dorsal cavity; a, the spinal…

Ciliated epithelium from the human trachea, highly magnified. Labels: a, large ciliated cell; d, cell, with two nuclei. "In ciliated epithelium the cells, which are generally columnar in shape, bear at their free extremities little hair-like processes which are agitated incessantly with a lashing or vibrating motion. These minute and delicate processes are named cilia, and may be regarded as active prolongations of the cell-protoplasm." —Kimber, 1907

Ciliated Epithelium Cells

Ciliated epithelium from the human trachea, highly magnified. Labels: a, large ciliated cell; d, cell,…

"When the concave mirror is large, say six inches in diameter, and eight or ten inches focal distance, it exhibits the human face of enormous bulk, the spectator being frightened at the size and courseness of his own features." -Comstock 1850

Magnified Face in a Concave Mirror

"When the concave mirror is large, say six inches in diameter, and eight or ten inches focal distance,…

The bony and cartilaginous skeleton.

Human Skeleton, Showing Bony and Cartilage Tissue

The bony and cartilaginous skeleton.

Wall of human stomach. Labels: E, epithelium; G, glands; Mm, muscularis mucosae.

Stomach Wall

Wall of human stomach. Labels: E, epithelium; G, glands; Mm, muscularis mucosae.

Red corpuscles (blood cells) of the frog. The red blood cells of birds, reptiles, amphibians and fishes are oval and contain a nucleus in the center that is not found in human red corpuscles.

Blood Cells

Red corpuscles (blood cells) of the frog. The red blood cells of birds, reptiles, amphibians and fishes…

"The human eye-essential parts shown in section." —Croft 1917

Eye

"The human eye-essential parts shown in section." —Croft 1917

"If the coin were to be observed in an empty pan and then watched as the pan was filled with water, the image of the coin would be refracted to position N." —Quackenbos 1859

Refraction as seen by the Human Eye

"If the coin were to be observed in an empty pan and then watched as the pan was filled with water,…

Structure of the human retina, showing the various layers.

Structure of the Retina

Structure of the human retina, showing the various layers.

Teeth of an herbivore, showing the rough surface of some of these teeth. Herbivores have no tearing teeth. Instead they have two kinds of teeth, cutting teeth in the front and grinding teeth in the back. This figure shows a peculiar arrangement of the enamel, which admirably fits them to grind up the fibers of the grass in the back grinding teeth of an herbivore. The enamel is not only on the outside as it is in human teeth, rather there are ridges on it standing up in the middle of each tooth.

Teeth of an Herbivore

Teeth of an herbivore, showing the rough surface of some of these teeth. Herbivores have no tearing…

Diagram of the human nervous system showing the brain, spinal cord, and nerves.

Nervous System

Diagram of the human nervous system showing the brain, spinal cord, and nerves.

The human skeleton.

Human Skeleton

The human skeleton.

The human skull, showing the bones of the head. <em>a</em>is the large bone of the forehead known as the frontal bone; <em>b</em> is known as the parietal bone, and <em>c</em> is the temporal bone.

Skull

The human skull, showing the bones of the head. ais the large bone of the forehead known as…

The vertebra of a fish, which is very different from that of a human. It has but two processes, <em> f f </em>. In humans there is a single short spinous process behind, while the vertebra is round in front. But in the fish there are two quite long spinous processes, one in front and the other in the rear (which is above and below, respectively, when the fish is in water).

Vertebra of a Fish

The vertebra of a fish, which is very different from that of a human. It has but two processes, …

Views of the stomach. Labels: A. stomach (human). B. Same, anterior wall removed. C. Portion of stomach, pylorus and duodenum. D. Section through coats of stomach. E. Fundus of a cardiac gland. F. Epithelium from surface of stomach. G. Arterie sand veins of mucous membrane. w. Esophagus. 2. Duodenum. 3. Pylorus. $. Cardia. 5. Lesser curvature. 6. Greater curvature. 7. Anterior surface. 8. Pyloric valve. 9. Mucous membrane, with rugae. 10. Inner surface of gastric mucous membrane. 11. Mucous membrane of duodenum with villi. 12. Pyloric gastric glands. 13. Circular or deep muscular fibers. 17. Mucous membrane. 18. Muscularis mucosae. 19. Submucous coat. 20. Circular muscular layer. 21. Longitudinal muscular layer. 22. Serous coat. 23. Orifice of gland. 24. Fundus of gland.

Views of the Stomach

Views of the stomach. Labels: A. stomach (human). B. Same, anterior wall removed. C. Portion of stomach,…

1. Dentition (teeth) of man. 2. Dentition of hyena. 3. Dentition of pig. 4. Dentition of Patagonian cavy (type of rodent). 5. Section of skull of Indian elephant, showing dentition of right side. 6. Crown of upper molar of horse, showing enamal folds. 7. Grinding surface of molar of African elephant, with enamal folds. 8. Single tooth of blue shark. 9. Longitudinal section of human tooth. 1. Incisors (human); C, canines; P, premolars; M, molars. a, enamel; b, dentine; c, cement (crusta petrosa); d, pulp cavity.

Teeth of Man and Several Animal Species

1. Dentition (teeth) of man. 2. Dentition of hyena. 3. Dentition of pig. 4. Dentition of Patagonian…

Every human body begin as a single nucleated cell. This cell, known as the ovum, divides or segments and gives rise to a mass consisting of a number of similar units known as the morula. At this stage there are no distinguishable tissues.

Cell Development

Every human body begin as a single nucleated cell. This cell, known as the ovum, divides or segments…

Portion of a human muscle fiber.

Portion of a Muscle Fiber

Portion of a human muscle fiber.

The human skeleton.

The Human Skeleton

The human skeleton.

The muscles of the human body.

Muscles of the Human Body

The muscles of the human body.

Diagram of the structure of the human retina. Labels: I, pigment layer; II, rod and cone layer; R, rods; C, cones; III-IX, intraretinal nerve-elements; X, axons which pass to optic nerve.

Retinal Structure

Diagram of the structure of the human retina. Labels: I, pigment layer; II, rod and cone layer; R, rods;…

General view of the human body - front view.

The Human Body - Front View

General view of the human body - front view.

General view of the human body - back view.

The Human Body - Back View

General view of the human body - back view.

Human liver cells.

Liver Cells

Human liver cells.

The human skeleton.

Human Skeleton

The human skeleton.

Image of teeth in a human jaw. "1, incisors; 2, canine; 3, bicuspids; 4, molars (the molar at the left is the "wisdom tooth); 5, a blood vessel; 6, a nerve." -Foster, 1921

Teeth

Image of teeth in a human jaw. "1, incisors; 2, canine; 3, bicuspids; 4, molars (the molar at the left…

Transverse section of the human kidney: "(a) cortex; (b) medulla; (c) small branch of the renal artery; (d) renal artery; (e) ureter; (f) pelvis." -Foster, 1921

Kidney

Transverse section of the human kidney: "(a) cortex; (b) medulla; (c) small branch of the renal artery;…

"A salt-water mollusk, highly esteemed as an article of food." -Foster, 1921.

Oyster

"A salt-water mollusk, highly esteemed as an article of food." -Foster, 1921.

A covered human-powered wagon used in Eastern countries where passengers were inside while two men would carry the poles of the palanquin on their shoulders.

Palanquin

A covered human-powered wagon used in Eastern countries where passengers were inside while two men would…

Front view of the human skeleton.

Skeleton, Front View

Front view of the human skeleton.

The skull and upper jaw of an early rhinoceros-like mammal from the Cenozoic time.

Dinoceras Mirabile

The skull and upper jaw of an early rhinoceros-like mammal from the Cenozoic time.

"A, embryonic cells from onion root tip; d, plasmatic membrane; c, cytoplasm; a, nuclear membrane enclosing the thread-like nuclear reticulum; b, nucleolus; e, plastids (black dots scattered about)." -Stevens, 1916

Onion Cells

"A, embryonic cells from onion root tip; d, plasmatic membrane; c, cytoplasm; a, nuclear membrane enclosing…

"B, older (onion) cells farther back from the root tip. The cytoplasm is becoming vacuolate; f, vacuole." -Stevens, 1916

Onion Cells

"B, older (onion) cells farther back from the root tip. The cytoplasm is becoming vacuolate; f, vacuole."…

In onion cells: "C, a cell from the epidermis of the mid-rib of Tradescantia zebrina, in its natural condition on the right, and plasmolyzed by salt solution on the left; g, space left by the recedence of the cytoplasm from the wall; the plasma membrane can now be seen as a delicate membrane bounding the shrunken protoplast." -Stevens, 1916

T. Zebrina Cell

In onion cells: "C, a cell from the epidermis of the mid-rib of Tradescantia zebrina, in its natural…

"A, cell from the epidermis of the upper side of the calyx of Tropaeolum majus with crystalline chromoplasts." -Stevens, 1916

T. Majus Cell

"A, cell from the epidermis of the upper side of the calyx of Tropaeolum majus with crystalline chromoplasts."…

"B, cells from the petal of Lupinus luteus with yellow chromoplasts." -Stevens, 1916

L. Luteus Cell

"B, cells from the petal of Lupinus luteus with yellow chromoplasts." -Stevens, 1916

"C, cell showing numerous chloroplasts scattered through the cytoplasm." -Stevens, 1916

Plant Cell

"C, cell showing numerous chloroplasts scattered through the cytoplasm." -Stevens, 1916

First stage in plant cell division: Protophase 1; "Resting cell ready to begin division." -Stevens, 1916

Plant Cell Division 1

First stage in plant cell division: Protophase 1; "Resting cell ready to begin division." -Stevens,…

Second stage in plant cell division: Protophase 2; "the nuclear reticulum is assuming the form of a thickened thread, and the cytoplasm at opposite poles is becoming thread-like to form the spindle fibers." -Stevens, 1916

Plant Cell Division 2

Second stage in plant cell division: Protophase 2; "the nuclear reticulum is assuming the form of a…

Third stage in plant cell division: Protophase 3; "The nuclear thread has divided longitudinally throughout the middle, and the spindle fibers have become more definite." -Stevens, 1916

Plant Cell Division 3

Third stage in plant cell division: Protophase 3; "The nuclear thread has divided longitudinally throughout…

Fourth stage in plant cell division: Protophase 4; "The nuclear membrane and the nucleolus have disappeared, and the nuclear thread has become segmented into chromosomes which are assembling at the equator of the cell." -Stevens, 1916

Plant Cell Division 4

Fourth stage in plant cell division: Protophase 4; "The nuclear membrane and the nucleolus have disappeared,…

Fifth stage in plant cell division: Metaphase; "The metaphase, where the longitudinal halves of the chromosomes are being drawn apart preparatory to their journey toward opposite poles." -Stevens, 1916

Plant Cell Division 5

Fifth stage in plant cell division: Metaphase; "The metaphase, where the longitudinal halves of the…

Sixth stage in plant cell division: Anaphase; "The anaphase, or movement of the chromosomes toward the poles, is about completed, connecting fibers extend from pole to pole." -Stevens, 1916

Plant Cell Division 6

Sixth stage in plant cell division: Anaphase; "The anaphase, or movement of the chromosomes toward the…

Seventh stage in plant cell division: Telophase; "Telophase where the chromosomes have begun to spin out in the form of a nuclear reticulum. The connecting fibers have begun to thicken in the equatorial plane." -Stevens, 1916

Plant Cell Division 7

Seventh stage in plant cell division: Telophase; "Telophase where the chromosomes have begun to spin…

Eighth stage in plant cell division: "The connecting fibers have spread out and come into contact with the wall of the mother cell in the equatorial plane, and the thickening of the fibers throughout this plane has made a complete cell plate within which the dividing wall will be produced." -Stevens, 1916

Plant Cell Division 8

Eighth stage in plant cell division: "The connecting fibers have spread out and come into contact with…

Ninth and final stage in plant cell division: "A nuclear membrane has been formed about each daughter nucleus, and the dividing cell-wall is complete." -Stevens, 1916

Plant Cell Division 9

Ninth and final stage in plant cell division: "A nuclear membrane has been formed about each daughter…

"Formation of endosperm in the embryo-sac of Agrimonia Eupatorium. Cell-walls are being formed between the nuclei." -Stevens, 1916

A. Eupatorium Cell

"Formation of endosperm in the embryo-sac of Agrimonia Eupatorium. Cell-walls are being formed between…

"Free cell formation of spores in the ascus of Erysiphe communis. A, ascus with single nucleus; C, cytoplasm; N, nucleus; NL, nucleolus; B, successive stages in nuclear division with the ascus; at X, early anaphase, nuclear membrane, NM, still persisting; R, kinoplasmic radiations from the poles; at Y, telophase, new nuclear membrane not yet formed; Z, a later stage where the nuclear membranes demark the daughter nuclei." -Stevens, 1916

E. Communis Cell

"Free cell formation of spores in the ascus of Erysiphe communis. A, ascus with single nucleus; C, cytoplasm;…

"Various stages of cell multiplication by budding of Saccharomyces cerevisiae." -Stevens, 1916

S. Cerevisiae Cell Multiplication

"Various stages of cell multiplication by budding of Saccharomyces cerevisiae." -Stevens, 1916

"Nucleus dividing by simple constriction. From the lining of the embryo-sac of Vicia faba." -Stevens, 1916

V. Faba Nucleus Division

"Nucleus dividing by simple constriction. From the lining of the embryo-sac of Vicia faba." -Stevens,…

"Diagram showing the evolution of tissues from the primordial meristem down to the beginning of cambial activity." -Stevens, 1916

Plant Tissues

"Diagram showing the evolution of tissues from the primordial meristem down to the beginning of cambial…

The epidermis of an oak leaf.

Plant Epidermis

The epidermis of an oak leaf.

The epidermis of an iris leaf.

Plant Epidermis

The epidermis of an iris leaf.

"Group of cells from petal of Viola tricolor." -Stevens, 1916

Plant Epidermis

"Group of cells from petal of Viola tricolor." -Stevens, 1916

"Two epidermal cells in cross section showing thickened outer wall differentiated into three layers, namely, an outer cuticle, cutinized layer (shaded), and an inner cellulose layer." -Stevens, 1916

Plant Epidermis

"Two epidermal cells in cross section showing thickened outer wall differentiated into three layers,…

"Epidermal outgrowths in the form of scales and hairs." -Stevens, 1916

Plant Epidermis

"Epidermal outgrowths in the form of scales and hairs." -Stevens, 1916