Cathode

The negative pole or electrode - i. e., the pole by which the electric current leaves.

Cellulose

The substance of which vegetable cell walls are formed.

Centrifugal

Efferent.

Centripetal

Afferent.

Cerebral Vesicles

Primitive swellings on the primary neural tube of the early embryo which develop into the brain.

Chemical Elements

Substances which cannot be split up into components, and therefore are regarded as simple.

Chlorophyll

The green coloring matter of the cells of plants. It is supposed to be the agent which, under the influence of light, decomposes carbon dioxide and water to form the cellulose and starch of the plant.

Cholesterin

A substance occurring in the bile, white matter of the brain and spinal cord, and in small quantities in many other tissues. Chemically it is a monatomic alcohol.

Chorda Dorsalis

The precursor of the vertebral column of the embryo.

Chorion

The outer layer of the membranes of the ovum, part of which becomes vascular, and helps to form the placenta.

Choroid

The vascular coat of the eyeball.

Chromatic Aberration

The alteration of white light into prismatic colors during its passage through an ordinary lens.

Chyle

The fluid absorbed from the small intestines by the lacteals.

Chyme

The fluid absorbed by gastric digestion.

Cilia

Minute vibratile processes which occur on the surface cells of the respiratory and many other epithelial membranes.

Circumvallate

Large papillae situated at the back of the tongue. They are surrounded by a fossa in the walls of which lie taste buds.

Cloaca

The opening common to the genko-urinary organs in the primitive hind gut of the embryo. The cloaca persists in birds.

Colloid

That condition of quasi-dissolved matter in which it will not diffuse through a membrane such as parchment. The opposite of crystalloid.

Colostrum

The first milk secreted alter delivery.

Coordination

The adjustment of separate actions for a definite result, as when the nerve centres cause various distinct muscles to act together and produce complex movements.

Curara

A poison causing motor paralysis by impairing the function of the nerve terminals.

Cytod

A living protoplasmic unit which has no nucleus.

Decidua Refiexa

The outgrowth of the uterine mucous membrane which surrounds the ovum.

Decidua Serotina

That part of the modified mucous membrane of the uterus in which the fecundated ovum is lodged.

Decidua Vera

The altered mucous membrane of the uterus, which lines that organ during gestation.

Deglutition

The act of swallowing.

Desquamation

The term used to denote the casting off of the outer layer of the skin.

Dialysis

The diffusion of soluble crystalloid substances through membranes, such as parchment.

Diastole

The period of relaxation and rest of the heart's muscle.

Dicrotic

The double wave of the arterial pulse. The dicrotic wave is seen on the descending part of the pulse curve.

Dioptric Media

Transparent bodies, such as those parts of the eye which so refract the light that images come to a focus on the retina.

Discus Proligerus

Part of the granular layer of the Graafian follicle surrounding the ovum.

Distal

A term used to denote a part relatively far from the centre.

Ductus Arteriosus

A short bond of union between the pulmonary artery and the aorta, which in the foetus carries blood from the right side of the heart into the aorta.

Ductus Venosus

A vessel which, in the foetus, carries blood from the umbilical vein to the vena cava. After birth it becomes a fibrous cord.

Ductus Vitello-Intestinalis

The union between the yolk sac and the intestine of the embryo.

Dyspnoea

Difficulty in breathing; a condition in which inordinate respiratory movements are excited by an unusually venous state of the blood in the respiratory nerve centre.

Ectoderm

The outer layer of simple organisms.

Ectosarc

The outer layer or covering of certain unicellular organisms.

Electrodes

The terminals which are applied to a substance in order to complete the circuit in passing a current through it.

Electrotonus

A peculiar electric state of nerves resulting from the passage of a continuous current through them.

Embryo

The name given to the animal at the earliest period of its development.

Emmetropic

A term applied to the normal eye, in which parallel rays of light are brought to a focus at the retina without accommodation.

Emulsification

The suspension of very fine particles in a liquid unable to dissolve them.

Endoderm

The inner layer of simple organisms.

Endogenous Reproduction

The formation of new cells or organisms within the body of the parent individual.

Endolymph

The liquid contained within the membranous labyrinth of the ear.

Endosarc

The inner layer of certain unicellular organisms.

Endosmosis

The diffusion of a fluid into a texture.

Endothelium

The single layer of thin cells lining the serous cavities, lymphatic and blood-vessels, and all spaces in the connective tissues (meso-blastic lining cells).

Epiblast

The uppermost of the three layers of the blastoderm, from which are developed the epidermis and the nerve centres.

Epithelium

The non-vascular cellular tissue developed from the epi- and hypoblast of the blastoderm.

Eupncea

A term used to denote the normal rhythm of respiratory movements in contradistinction to dyspnoea and apncea.

Excito-Motor