1891.] MICROSCOPICAL JOURNAL. 153 



Introduction to Elementary Biology. 



By henry L. OSBORN, 



HAMLINE, MINN. 



Part II.— The Cell. 



( Continued from pciire 127) 



Not the least wonderful peculiarity of protoplasm is the multitudinous 

 shapes and associations in which we know it. The bodies of all the 

 higher animals and plants are composed of elements or imits called cells, 

 each of which is or has at some time been a minute mass of protoplasm 

 and products manufactured by protoplasm. In their earliest history 

 all cells, however much they grow to differ, are minute globules usually 

 nearly or quite spherical and filled with protoplasm. The cell is coated 

 with a very thin envelope called the cell-wall, the chemical nature of 

 which is the same in nearly all animal cells, and is albuminous, and in 

 all plant cells is starchy. In the centre of the protoplasm there lives a 

 denser body called the nucleus, which is marked ofl'from the remaining 

 protoplasm by a distinct boundary line. The nucleus is composed of 

 protoplasm, but of a kind not wholly like that of the cell at large. The 

 nucleus, the protoplasm, and the cell-wall are thus the component parts 

 of all young cells. Fully grown cells difler very much in regard to the 

 protoplasmic powers they exercise most, some becoming chronic meta- 

 bolizei's, while others are equally habitual in the exercise of the powers 

 of motion or irritability. Cells which thus specialize one or other 

 of these powers have shapes to match, and it thus becomes possible to 

 infer the action of a cell from its shape. Sometimes cells produce by 

 metabolism certain chemical substances which they store away inside 

 the cell-wall, enlarging the wall for the purpose of forming spaces called 

 '' vacuoles" in the protoplasm for the reception of these products. Such 

 matter is called "formed" or "dead" matter in contrast with the 

 protoplasm, which is called "formative" or "living" matter. The 

 large bodies of animals and plants are aggregates of cells and of the 

 formed nature which the protoplasm has produced. Since all of these 

 can be produced from gases or liquids it is reasonable that they should 

 be returnable to that state from which they came, and this we know to 

 be true. 



Amoeba. — We shall do well, if we are to understand protoplasm 

 and its powers and products, to examine some specimen of live proto- 

 plasm, for though the chemist is denied the privilege of analyzing liv- 

 ing protoplasm, the biologist can spy upon its proceedings for indefinite 

 periods without destroying the substance. One might examine any of 

 a large number of specimens of living cells as our first specimen, but 

 we can begin very well with amoeba. This is found in stagnant, slimy, 

 warm fresh water. It is very minute and must be sought and studied 

 with a magnifying power of at least 300 diameters. It has been often 

 described and the reader should consult some of the fuller text-book 

 descriptions. We may briefly say that it is much the shape of a drop 

 of water which has fallen and spread out irregularly. It has a faint 

 translucent border enclosing a finely grained faintly yellowish substance. 

 The granular substance within is active protoplasm, a portion of which, 

 slightly difterent in character, is the boundary. No distinct cell-wall 



