This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Dyspnea is a slight lack of oxygen, sufficient to stimulate but not to depress the respiratory centers. Cyanosis, a bluish color of the skin, particularly of the face, then appearing. Apnea is a condition in which there is a period when no respiratory action takes place.
Abnormalities in the secretions of the organs may cause marked disturbance. The secretions may be either internal or external. The external pass directly from the glands by means of ducts. The internal pass slowly into the blood, which carries them to all parts of the body. In addition to the actions of the better known internal secretions are others, called hormones, whose functions appear to be to stimulate to full activity other digestive glands, even those situated at a distance.