392- THE HISTORY OF BIOLOGY 



of every cell there belongs, as an essential component, an "areola" or, as he 

 also calls it, a nucleus; this cell-component he discovered in the epidermis 

 of the Orchidaceas and later he established its existence in a great number of 

 other plant-cells. It was, however, reserved to other investigators to dis- 

 cover its true significance. 



Cytological research was given a new direction by Matthias Jacob 

 ScHLEiDEN, one of the strangest scientific personalities of his age. He was 

 born in Hamburg in 1804, the son of an eminent doctor. He began by study- 

 ing jurisprudence, became a doctor of law, and took up a practice as a barris- 

 ter in his native town. He had, however, but little success as a pleader, a 

 fact that increased his naturally melancholy disposition. Finally, in a fit of 

 despondency he shot himself in the forehead, but without the result he in- 

 tended; he recovered and then resolved to devote himself to natural science. He 

 became doctor of both philosophy and medicine, gained a great reputation by 

 his writings, and in 1850 became professor of botany at Jena. After twelve 

 years, however, he resigned; a professorship at Dorpat, to which he was 

 appointed shortly afterwards, he relinquished within the year and after that 

 led a life of wandering, with brief sojourns in various German towns, which 

 lasted till his death, in 1881. The life he led fully testifies to a soul without 

 balance, and this is reflected in more ways than one in his scientific work. 



The work that at once brought Schleiden fame was an essay in Miiller's 

 archives of the year 1838 entitled "Beifrage xur Phytoge^zesis.'' The question he 

 propounds is: How does the cell arise? Here Schleiden takes as his starting- 

 point Brown's above-mentioned discovery of the cell-nucleus, and his service 

 to science lies in the fact that he was able to appreciate its fundamental 

 importance, which Brown himself failed to do. From the nucleus, or, as he 

 calls it, the cytoblast, Schleiden sought to reconstruct the course of develop- 

 ment of the cell, and he made a very happy choice when he selected for the 

 purpose the embryonic cell as his starting-point. He made a special study of 

 the embryo-sac in different phanerogams, carefully examining the nuclei in the 

 cells in question, and discovered in them the formation that is now termed the 

 nucleolus or nucleal body. This discovery, however, led him to continue 

 the investigation along the wrong lines; he thought he had discovered that 

 the nucleolus is first formed through an accumulation of granulate mucus in 

 the uniform content of the embryo-sac and he believes it to consist of gum; 

 around this element is afterwards stratified the rest of the nucleus, and not 

 until the latter is complete is there formed on its surface a small vesicle that 

 grows outwards until it encloses the entire nucleus; the walls of the vesicle 

 thicken, and thereby the cell becomes complete. According to Schleiden, 

 during the further development of the cell the nucleus is in most cases dis- 

 solved — a statement that of course does not accord with the facts. As will 

 be seen, the whole of this cell-formation theory is quite out of keeping with 



