The Prolongation of Life: Optimistic Studies. Élie Metchnikoff
to high notes and slight deafness for low notes. Dr. Löwenberg attributed these changes to senile degeneration of the ear which affected more and more seriously the nervous mechanism although it had caused little change in the conducting apparatus. Notwithstanding her physical weakness, Mme. Robineau retained her intelligence fully, her mind remained delicate and refined and the goodness of her heart was touching. In contrast with the usual selfishness of old people, Mme. Robineau took a vivid interest in those around her. Her conversation was intelligent, connected, and logical. Examination of the physical functions of this old lady revealed facts of great interest. Dr. Ambard found that the sounds of the heart were normal, but perhaps a little accentuated. The pulse was regular, 70 to 84 a minute, and its tension was normal. The arterial pressure was 17. The lungs were sound. All these facts testify to her general health. The most remarkable circumstance was the absence of sclerosis of the arteries, although such degeneration is usually believed to be a normal character of old age.
Analysis of the urine, made on several occasions, showed that the kidneys were affected with a chronic disease, which, however, was not serious.2
Although the sense of taste was weak, Madame Robineau had a fair appetite. She ate and drank little, but her diet was varied. She took butcher’s meat or chicken extremely seldom, but ate eggs, fish, farinaceous food, vegetables, and stewed fruit, and drank sweetened water with a little white wine, and sometimes, after a meal, a small glass of dessert wine. The processes of alimentary digestion and excretion were normal.
It has sometimes been thought that duration of life is a hereditary property. There was no evidence for this in the present case. Madame Robineau’s relatives had died comparatively early in life, and a centenarian was unknown in her family. Her great age was an acquired character. Her whole life had been extremely regular. She had married a timber merchant, and had lived for many years in a suburb of Paris in comfortable circumstances. Her character was gentle and affectionate; she was thoroughly domesticated, and had been devoted to home life with very few distractions.
At the age of 106 years, her intelligence suddenly became weak. She lost her memory almost completely, and sometimes wandered. But her gentle and affectionate disposition remained unaltered.
The appearance of aged persons is too well known to make detailed description necessary. The skin of the face is dry and wrinkled and generally pale; the hairs on the head and the body are white; the back is bent, and the gait is slow and laborious, whilst the memory is weak. Such are the most familiar traits of old age. Baldness is not a special character; it often begins during youth and naturally is progressive, but if it has not already appeared, it does not come on with old age.
The stature diminishes in old age. As the result of a series of observations, it has been established that a man loses more than an inch (3·166 cm.), and a woman more than an inch and a half (4·3 cm.), between the ages of fifty and eighty-five years. In extreme cases, the loss may be nearly three inches. The weight also becomes less. According to Quételet, males attain their maximum weights at the age of forty, females at that of fifty. From the age of sixty years onwards, the body becomes lighter, the loss at eighty being as much as thirteen pounds.
Such losses of height and weight are signs of the general atrophy of the aged organism. Not merely the soft parts, such as the muscles and viscera, but even the bones lose weight, in the latter case the loss being of the mineral constituents. This process of decalcification makes the skeleton brittle, and is sometimes the cause of fatal accidents.
The loss of muscular tissue is specially great. The volume diminishes, and the substance becomes paler; the fat between the fibres is absorbed, and may disappear completely. Movements are slower, and the muscular force is abated. This progressive degeneration has been examined by dynamometrical measurements of the hand and the trunk, and is greater in males than in females.
The volumes and weights of the visceral organs similarly become smaller, but the diminution is not uniform.
The old age of lower mammals presents characters similar to those found in man. I can now give other instances than the case of the old dog which I described in the “Nature of Man.”
I will first take the case of old elephants, described by a competent observer. “The general appearance is wretched, the skull being often hardly covered with skin; there are deep abrasions under the eyes, and smaller ones on the cheeks, whilst the skin of the forehead is very often deeply fissured or covered with lumps. The eyes are usually dim, and discharge an abnormal quantity of water. The margin of the ears, specially on the lower side, is usually frayed. The skin of the trunk is roughened, hard, and warty, so that the organ has lost much of its flexibility. The skin on the body generally is worn and wrinkled; the legs are thinner than in maturity, the huge mass of muscles being much shrunken, whilst the circumference, especially just above the feet, is considerably reduced. The skin round the toe-nails is roughened and frayed. The tail is scaly and hard, and the tip is often hairless.
Fig. 2.—A Mare, thirty-seven years old.
Fig. 3.—A White Duck, which lived for more than a quarter of a century.
Horses begin to grow old much sooner than elephants. I reproduce (Fig. 2) the photograph of a rare instance of longevity, a mare 37 years old, which belonged to M. Métaine, in the department of Mayenne. The skin, bare in places, but elsewhere covered with long hairs, shows considerable atrophy. The general attitude reveals the feebleness of the whole body. Many birds, on the other hand, show at similar ages very slight external change, as may be seen from the photograph of a duck more than 25 years old (Fig. 3) which belonged to Dr. Jean Charcot. At a still greater age, as may be seen occasionally in parrots, the general debility of the body reveals itself in the attitude, in the condition of the feathers, and in the swelling of the joints. On the other hand, the oldest reptiles which have been observed do not differ in appearance from normal adults of the same species. I have in my possession a male tortoise (Testudo mauritanica) given me by my friends MM. Rabaud and Caullery, and which is at least 86 years old. It shows no sign of old age, and in all respects behaves like any other individual of this species. More than 31 years ago it was wounded by a blow, the traces of which remain visible on the right side of the carapace (Fig. 4). In the last three years the tortoise lived in a garden at Montauban, along with two females which laid fertile eggs. The old male, although, as I have said, probably at least 86 years of age, was still sexually healthy.
Fig. 4.—An Old Land-tortoise.
I have borrowed from the interesting volume of Prof. Sir E. Ray Lankester3 the figure (Fig. 5) and description of a giant tortoise from the island of Mauritius, which is probably the oldest of all living animals. It was brought to Mauritius from the Seychelles in 1764, and has lived since then in the garden of the Governor, and as it has thus already been 140 years in captivity, its age must be at least 150 years, although we have not exact information. Notwithstanding this, it shows no signs of old age.
The examples which I have brought together show that often amongst vertebrates there are some animals the organisms of which withstand the ravages of time much better than that of man. I think it a fair inference that senility, the precocious senescence which is one of the greatest sorrows of humanity, is not so profoundly seated in the constitution of the higher animals as has generally been supposed. It is not necessary, therefore, to discuss at length the general question as to whether senile degeneration is an inevitable event in living organisms.