_Somatic and Sexual Cells._—In this sense we may say with Weismann that there are two things in the animal and in man—the one mortal, the _soma_ the body, the other immortal, the _germen_. These germinal cells, as in the case of the protozoa we mentioned above, possess a conditional immortality. They are imperishable, but on the contrary, are fragile and vulnerable. Millions of ova are destroyed and are disappearing every moment. They may die by accident, but never of old age. We now understand that if the protistae are immortal, it is because these living beings, reduced to a single cell, accumulate in it the compound characters of the somatic cell and germinal cell, and enjoy the privilege which is attached to the latter. CHAPTER VII. MAN. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH. The miseries of humanity: 1. Disease; 2. Old age.—Old age considered as a chronic disease.—Its occasional cause.—3. The disharmonies of human nature; 4. The instinct of life and the instinct of death. Man’s unhappy plight is the constant theme of philosophies and religions. Without referring to its moral basis, it has a physical basis due to four causes—the physical imperfection or disharmony of nature, disease, old age, and death—or rather of three, for what we call old age is perhaps a simple disease. These are the great sorrows of man, the sources of all his woes. Disease attacks him, old age awaits him, and death must tear him from all the ties which he has formed. All his pleasures are poisoned by the certain knowledge that they last but for a moment, that they are as precarious as his health, his youth, and his life itself. § 1. DISEASE. Disease, frequent, constant, and inevitable as it is, is, however, nothing but a fact outside the natural order. Its character is clearly accidental, and it interrupts the normal cycle of evolution. Medical observation teaches us, on the other hand, that the health of the body reacts on that of the mind; and therefore man as a whole, moral and physical, is affected by disease. Bacon described a diseased body as a jailer to the soul, and the healthy body as a host. Pascal recognized in diseases a principle of error. “They spoil our judgment and our senses.”