Describe the Sweat-glands. Each gland consists of a single convoluted tube, situated usually in the subcutaneous cellular tissue, and opening on the surface of the integument by a spiral duct which pierces the derma and the epidermis. It is formed of two coats, an external fibro-cellular, which is continuous with the corium, and an epithelial lining, continuous with the epidermis.

State the probable number of Sweat-glands and their Evaporating area. They are estimated as varying, in different parts of the integument, from 417 to 2800 to the square inch, giving for the whole body a total of nearly two millions and a half, representing an evaporating surface of about 8 square inches.

ORGANS OF TASTE.

What are the special Organs of Taste? The Taste buds, small, flaskshaped bodies, each about inch long, situated in the fungiform and circumvallate papillæ of the tongue. The seat of the sense of taste lies, however, in the mucous membrane covering the dorsum of the tongue, the upper portion of the pharynx, the soft palate and the fauces.

Name the special Nerves of Taste in the Tongue. The—

Chorda Tympani Branch of the Facial,—for its anterior two-thirds; perceiving saline, acid and styptic qualities (Flint).

Lingual Branch of the Glosso-pharyngeal,—for its posterior third; appreciating alkaline, metallic, sweet and bitter tastes (Flint).

What is Sapolini's view of the Chorda Tympani Nerve? From repeated dissections, Dr. Sapolini, of Milan, believes the chorda tympani to be a separate cranial nerve, having its proximal end in the so-called intermediary nerve of Wrisberg, originating in the floor of the 4th ventricle, and terminating in a dense plexus with the lingual branch of the 5th nerve, in the muscles of the tongue. He further concludes that the chorda tympani is the nerve governing the movements of the tongue in speech, and that the nerves of taste are the Lingual Branches of the 5th and 9th nerves.

THE NOSE.

[For an osteological description of the Nasal Fossæ and Septum, see page 31.]

Where is the Organ of Smell situated? In the mucous lining of the upper portion of the nasal fosse, which is the seat of distribution of the terminal filaments of the Olfactory Nerve,d the special nerve of the sense of smell.

What is the Schneiderian Membrane? The Schneiderian or Pituitary Membrane is the mucous membrane of the nasal fossæ. It is continuous with

the mucous lining of the pharynx, Eustachian tube, tympanum and mastoid cells; also with that of the frontal, ethmoidal and sphenoidal sinuses, the antrum, nasal duct, and the conjunctiva. It is covered with columnar epithelium, ciliated throughout most of its extent, provided with mucous glands, and in

Name the Arteries of the Nose. They are the

Lateralis Nasi,-branch of the facial, to the ale of the nose.

Nasal of the Septum,-from the superior coronary artery, to the septum. Nasal,-branches of the ophthalmic and infra-orbital, to the dorsum and sides of the nose.

Name the Arteries of the Nasal Fossæ. They are theAnterior and Posterior Ethmoidal,-from the ophthalmic. Spheno-palatine,-branch of the internal maxillary.

Alveolar,-branch of the internal maxillary, to the antrum.

What Nerves supply the Nose? Branches from the facial, infraorbital and infra-trochlear, and a filament from the nasal branch of the ophthalmic nerve.

What Nerves supply the Nasal Fossæ? They are the

Olfactory or 1st Cranial,e-over the upper third of the septum nasi, and over the superior and middle turbinated bones.

Nasal Branch of the Ophthalmic,g—to the septum and outer walls.

Anterior Dental Branch of the Superior Maxillary,j-to the inferior meatus of the nose and the inferior turbinated bone.

Spheno-palatine Ganglion,-sends branches to the septum and the superior turbinated bone,-the Superior Nasal Br. to the same parts,-the Nasopalatine to the middle of the septum,-and the Anterior Palatine to the middle and lower turbinated bones.

THE EYE.

[For an osteological description of the Orbit, see page 29.]

What is the Visual Apparatus? It comprises the eyeballs and their appendages, which collect the luminous impressions,—and the optic nerves, which convey these impressions to the brain.

Describe the Eyeball. It is a spherical organ, situated in the anterior part of the orbital cavity, on a cushion of connective tissue and fat, where it is retained by its muscles, the optic nerve, the conjunctiva, etc., and protected in front by the eyelids and eyebrows. Projecting from its anterior surface is the segment of a smaller, transparent sphere, the Cornea. The eyeball has the following

Diameters,-Antero-posterior, about .95 inch,-Transverse, .92 inch,— Vertical, .90 inch,-in the adult.

Anterior Pole,-is the geometric centre of the cornea.

Posterior Pole,—is the geometric centre of the fundus.

Optic Axis, is an imaginary straight line connecting the poles.

Visual Axis,—an imaginary straight line from the yellow spot to the object, through the nodal point. It cuts the cornea above the optic axis, at an angle therewith of 3° to 7°, the Visual Angle.

Nodal Point, the centre of curvature of the refracting surfaces.

Equatorial Plane,—an imaginary plane through the centre of the eyeball, perpendicular to the axis, dividing the ball or globe into the anterior and posterior hemispheres. The Equator is the line where this plane cuts the surface of the globe.

Meridional Planes,—are imaginary planes coinciding with the axis of the eyeball. Meridians are the lines where these planes intersect the surface of the globe.

Describe the Tunica Vaginalis Oculi. It is a fibrous capsule, surrounding the eyeball and the intra-orbital portion of the optic nerve; arising from the optic foramen and being lost anteriorly on the sclerotic. It consists of two layers (parietal and visceral) enclosing a lymph-space which communicates with the lymph-space between the sclerotic and choroid coats. The tendons of the ocular muscles pierce it. The

Capsule of Bonnet,—is the portion of tunica vaginalis posterior to the point where the tendons pass through it. This part is loosely attached to the eyeball, which rotates in it.

Capsule of Tenon,—is the portion of the tunica vaginalis anterior to the passage of the tendons. [The whole capsule or Tunica Vaginalis is by many anatomists named the Capsule of Tenon.]

Vitreous, 18-in the posterior chamber of the eyeball.

THE SCLEROTIC AND CORNEA.

Describe the Sclerotic. The Sclerotic or hard coat is the posterior fivesixths of the external tunic of the eyeball, the anterior one-sixth being the Cornea. Externally it is of a white color, covered anteriorly by the conjunctival mucous membrane, posteriorly being continuous with the sheath of the optic nerve. Internally its color is brown, and its surface marked by grooves for the ciliary nerves. The optic nerve pierces it posteriorly, also the long and short ciliary arteries, posterior ciliary veins and short ciliary nerves. In the equatorial region it is pierced obliquely by the venæ vorticosæ, and around the corneal border by the anterior ciliary arteries and veins. It is composed of connective tissue with elastic fibres, intermixed with pigment cells, and cells resembling the corneal corpuscles. It presents for consideration the following points, viz. :

Thickness,-inch posteriorly, inch anteriorly.

Lamina Fusca, a layer of very fine connective tissue, connecting the sclerotic with the outer surface of the choroid.

Lamina Cribosa,-the posterior perforated portion of the sclerotic, which at this point is a thin, cribriform lamina. Its largest opening transmits the arteria centralis retinæ, and is named the Porus Opticus, or Optic Canal.

Sub-conjunctival Tissue,-connects the conjunctiva with the outer surface of the sclerotic.

Sulcus,-a slight circular depression around the junction of the sclerotic with the cornea.

Arteries, from the Ciliary, are few and in a coarse net-work, uniting at wide intervals, but forming, however, the

Posterior Vascular Zone, or Zone of Zinn,—an arterial zone around the optic nerve entrance, formed by twigs of the short ciliary going to the optic nerve to anastomose with branches of the central artery of the retina, forming the only connection between the ciliary and retinal systems. Anterior Vascular Zone,-around the cornea, formed by sub-conjunctival branches of anterior ciliary vessels.

Nerves,-none have been yet found in the sclerotic.

What is the Cornea? The Cornea, or horny body, is the anterior transparent projecting portion of the external tunic of the eyeball, forming about one-sixth thereof. It is set into the sclerotic as a watch-crystal into its case, is of ellipsoidal base, the transverse diameter being the longest, and slightly more convex vertically than horizontally. Its

Thickness, is inch at centre, inch at periphery.
Index of Refraction,- 1.342.

Vessels,-none, except the peripheral zone, inch wide, formed of capillary loops from Episcleral branches of the anterior ciliary, which terminate at its circumference; so that it is practically a non-vascular structure. Nerves, are numerous; 20 or 30 twigs from the Ciliary nerves form an intricate plexus throughout its laminated substance.

Describe the Structure of the Cornea. It consists of five layers,—centrally the true corneal tissue, having in front an anterior elastic lamina and the conjunctival epithelium; behind, a posterior elastic lamina and the epithelial lining of the aqueous chamber. The

Layer of Conjunctival Epithelium go inch thick, consists of two or three layers of transparent nucleated cells.

Anterior Elastic Lamina, also named the Anterior Limiting Layer, the Membrane of Bowman or Membrane of Reichert,—is to inch thick, a firm, elastic and transparent homogeneous membrane, consisting of closely-interwoven fibrils, similar to those in the corneal tissue proper. True Corneal Tissue,- inch thick, a transparent, fibrous structure, formed of five connective-tissue fibrillæ, united in bundles, and these in laminæ, between which is a semi-fluid cement, filled with Corneal Corpuscles and wandering cells.

Posterior Elastic Lamina, Membrane of Descemet, or Demours,-is, like the anterior elastic lamina, a structureless basement membrane, of extreme thinness, resisting the action of water, alcohol or acids; very brittle, ex