There is only one constant element in immunity, whether innate or acquired, and that is phagocytosis. The extension and importance of this factor can no longer be denied.

Needless fear and panic over disease and misfortune that seldom materialize are simply bad habits. By proper ventilation and illumination of the mind it is possible to cultivate tolerance, poise and real courage.

It is possible to state as a general principle that the mesodermic phagocytes, which originally (as in the sponges of our days) acted as digestive cells, retained their role to absorb the dead or weakened parts of the organism as much as different foreign intruders.

The Greek conception of a life in harmony with nature found its most complete development in the rationalism of the Renaissance and of the centuries that followed it.

Science, it is said, no doubt has ameliorated the material conditions of human life, but is powerless to solve those moral and philosophical questions that interest cultured people so deeply.

Most of the centenarians whom I have been able to see have been so defective mentally that all that can be studied in them are the physical qualities and functions.

It is, of course, quite natural that a biologist whose attention had been aroused by noticing in his own case the phenomena of precocious old age should turn to study the causes of it.

Disease is not the prerogative of man and the domestic animals, so it was quite natural to see if the lower animals, with very simple organizations, showed pathological phenomena, and if so, infection, cure and immunity could be observed among them.

Whatever concerns health is of real public interest.

The old age of lower mammals presents characters similar to those found in man.