"The essential and fundamental condition of all respiration is the reciprocal action of the nourishing fluid, and a medium containing oxygen." Dumas believes that oxygen is necessary to the conservation of the vitality and proper structure of the globules of the blood; also that the integrity of these organisms is one of the essential conditions to the arterialization of the nourishing stream.
Milne Edwards, also, maintains that the great absorbing powers of the blood exist in the globules. The normal number of these globules is one hundred and twenty-seven out of the thousand component parts of the blood; but they vary according to the barometer of health; sometimes they are observed in disease to descend to sixty-five. Vierodt has shown how a certain limit in the number of blood globules in the mammalia cannot be passed in the descending scale without death taking place. Simon and others have also shown how a careful and nutritious regimen may increase these globules in the blood of the consumptive, bringing them up from sixty-four to even one hundred and forty-four.
The blood of man is the richest of all the mammalia, and it contains, according to Berzelius, three times as many hydrochlorates as the blood of the ox.
Its richness depends upon the species and individual, and also upon the degree of health, it varying according to the condition of the person.
"A diseased pathological condition causes a diminution in the proportion of active principles of the nourishing fluid, and especially in fibrine, of which the abundance is allied to the most important activity of the vital work in some parts of the organism." "The blood," says Dr. Jones, "is not only distributed by innumerable channels through every recess of the body; the blood is not only the source of all the elements of structure; the blood not only furnishes the materials for all the secretions and excretions, and for all the chemical changes,--but the blood is in turn affected by the physical and chemical changes of every vessel, of every nerve, of every organ and texture of the body. It is evident then that the constitution of the blood will depend upon the food, upon the vigor and perfection of the organs of digestion, respiration, circulation, secretion, and excretion; upon the vigor and perfection of the nervous system, and of all the organs and apparatus; and upon the correlation of the physical, vital, and nervous forces. The character of the blood will then vary with the animal; with the organ and tissue through which it is circulating; with the age, sex, temperament, race, diet, previous habits, occupation, and previous diseases; with the soil and climate; and with the relative states of the activity of the forces."