THE CELL-STATE. 181 



its work away from the indigo-plant by artificially producing indigo. 

 But a raw material which has at some time been brought forth out of 

 the laboratory of a living plant-cell always lies at the foundation of 

 all these manipulations of the chemist, wonderful as they are. And, 

 notwithstanding the immense progress that modern chemistry has 

 made within the last ten years, its art is still limited at this point : no 

 prospect yet exists that it will be able, artificially, to produce the most 

 important of all the substances that go to build up the bodies of ani- 

 mals and plants, and to form their living cell-tissues protoplasm, or 

 the envelope of the plant-cells, the matter of the muscles and nerves. 

 Chemistry shares this limitation of its means with animals. No animal 

 can live on air, water, and earth alone, like the plants ; no animal can 

 combine the simple chemical combinations, as they occur in lifeless 

 nature, into the life-substance protoplasm. The animal must draw the 

 substance of his flesh and blood from the plant, for his own vital forces 

 are not competent to produce it. The plant-cells alone possess the 

 faculty of ennobling the simple combinations of lifeless nature into 

 matter fitted for life. Every cell, furthermore, possesses another art, 

 that of forming different fabrics out of the same raw material. Hence 

 arises that infinite diversity of substances of different properties which 

 are drawn from the vegetable kingdom. Close together, in the shadow 

 of the same wood, grow crow-foot and wood-ruff, centaury and night- 

 shade ; the same soil gives food to their roots, the same air plays 

 around their foliage ; and yet the cells of one secrete a pungent, those 

 of another a narcotic poison, those of a third a bitter medicinal juice, 

 those of a fourth an aromatic flavor. The cell utilizes a part of its 

 food for its own growth ; but, sooner or later, the growth ceases, and 

 the cell, keeping the form and size it has acquired, becomes a per- 

 manent cell. It is round or oval, or resembles a many-sided crystal. 

 Some cells become flat and square, like a tile ; some put out rays, like 

 a star, or form a zigzag, like the wall of a fortress ; many lengthen 

 themselves out. The inner structure, also, of the cell changes with 

 age ; the envelope, delicate and thin in youth, afterward receives accre- 

 tions and ornaments. Some cells have within a hollow screw-way, like 

 a winding stair ; in others, the inside is covered with beautiful net- 

 tings, rings, flutings, or lattices. Most cells thicken their casings, as 

 the oyster does, by adding new layers over the older ones ; and, when 

 their hollows are quite filled up, they may rival stones and bones in 

 hardness, as, for example, the cells of the iron-wood and the ivory- 

 nut. 



As the cell-wall grows thicker, fluids and gases penetrate its invisi- 

 ble pores with more difficulty ; and with continuous increase of thick- 

 ness the living protoplasmic bodies inhabiting its interior must finally 

 die for want of food. They in effect build their own coffin, immure 

 themselves living in their own cell-prison. But a wonderful provision 

 prevents the food being entirely cut off. While the cell- wall is arch- 



