The mysterious process which physiologists call metamorphosis oftissue, or intestitial change, deserves attention in connection withour subject. It interests both sexes alike. Unless it goes onnormally, neither boys, girls, men, nor women, can have bodies orbrains worth talking about. It is a process, without which not a stepcan be taken, or muscle moved, or food digested, or nutrimentassimilated, or any function, physical or mental, performed. By itsaid, growth and development are carried on. Youth, maturity, and oldage result from changes in its character. It is alike the support andthe guide of health convalescence, and disease. It is the means bywhich, in the human system, force is developed, and growth and decayrendered possible. The process, in itself, is one of the simplest. Itis merely the replacing of one microscopic cell by another; and yetupon this simple process hang the issues of life and death, of thoughtand power.
Carpenter, in his physiology, reports the discovery, which we owe toGerman investigation, "that the whole structure originates in a singlecell; that this cell gives birth to others, analogous to itself, andthese again to many future generations; and that all the variedtissues of the animal body are developed from cells."[9] A more recentwriter adds, "In the higher animals and plants, we are presented withstructures which may be regarded as essentially aggregates of cells;and there is now a physiological division of labor, some of the cellsbeing concerned with the nutriment of the organism, whilst others areset apart, and dedicated to the function of reproduction. Every cellin such an aggregate leads a life, which, in a certain limited sense,may be said to be independent; and each discharges its own function inthe general economy. Each cell has a period of development, growth,and active life, and each ultimately perishes; the life of theorganism not only not depending upon the life of its elementalfactors, but actually being kept up by their constant destruction andas constant renewal."[10] Growth, health, and disease are cellularmanifestations. With every act of life, the movement of a finger, thepulsation of a heart, the uttering of a word, the coining of athought, the thrill of an emotion, there is the destruction of acertain number of cells. Their destruction evolves or sets free theforce that we recognize as movement, speech, thought, and emotion. Thenumber of cells destroyed depends upon the intensity and duration ofthe effort that correlates their destruction. When a blacksmith wieldsa hammer for an hour, he uses up the number of cells necessary toyield that amount of muscular force. When a girl studies Latin for anhour, she uses up the number of brain-cells necessary to yield thatamount of intellectual force. As fast as one cell is destroyed,another is generated. The death of one is followed instantly by thebirth of its successor. This continual process of cellular death andbirth, the income and outgo of cells, that follow each other like thewaves of the sea, each different yet each the same, is metamorphosisof tissue. This is life. It corresponds very nearly to Bichat'sdefinition that, "life is organization in action." The finer sense ofShakspeare dictated a truer definition than the science of the Frenchphysiologist
Carpenter, in his physiology, reports the discovery, which we owe toGerman investigation, "that the whole structure originates in a singlecell; that this cell gives birth to others, analogous to itself, andthese again to many future generations; and that all the variedtissues of the animal body are developed from cells."[9] A more recentwriter adds, "In the higher animals and plants, we are presented withstructures which may be regarded as essentially aggregates of cells;and there is now a physiological division of labor, some of the cellsbeing concerned with the nutriment of the organism, whilst others areset apart, and dedicated to the function of reproduction. Every cellin such an aggregate leads a life, which, in a certain limited sense,may be said to be independent; and each discharges its own function inthe general economy. Each cell has a period of development, growth,and active life, and each ultimately perishes; the life of theorganism not only not depending upon the life of its elementalfactors, but actually being kept up by their constant destruction andas constant renewal."[10] Growth, health, and disease are cellularmanifestations. With every act of life, the movement of a finger, thepulsation of a heart, the uttering of a word, the coining of athought, the thrill of an emotion, there is the destruction of acertain number of cells. Their destruction evolves or sets free theforce that we recognize as movement, speech, thought, and emotion. Thenumber of cells destroyed depends upon the intensity and duration ofthe effort that correlates their destruction. When a blacksmith wieldsa hammer for an hour, he uses up the number of cells necessary toyield that amount of muscular force. When a girl studies Latin for anhour, she uses up the number of brain-cells necessary to yield thatamount of intellectual force. As fast as one cell is destroyed,another is generated. The death of one is followed instantly by thebirth of its successor. This continual process of cellular death andbirth, the income and outgo of cells, that follow each other like thewaves of the sea, each different yet each the same, is metamorphosisof tissue. This is life. It corresponds very nearly to Bichat'sdefinition that, "life is organization in action." The finer sense ofShakspeare dictated a truer definition than the science of the Frenchphysiologist
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