g INTRODUCTION TO CYTOLOGY 



He sought to place botany on a scientific footing equal to that of physics 

 and chemistry, and insisted upon accurate observation and developmental 

 studies as the basis of morphology. Sachs says: "Endowed with some- 

 what too great love of combat, and armed with a pen regardless of the 

 wounds it inflicted, ready to strike at any moment, and very prone to 

 exaggeration, Schleiden was just the man needed in the state in which 

 botany then was." 



Theodor Schwann (1810-1882) was associated as a student with 

 Johannes Muller, the great physiologist, first at Wiirzburg and later at 

 Berlin. It was in the latter place that he put forth his statement of the 

 Cell Theory. Immediately afterward he went to Louvain, where he was 

 a professor for nine years, and later transferred to Liege. In disposition 

 he contrasted strongly with Schleiden, being described as "gentle and 

 pacific." 



It is said that Schleiden, while dining with Schwann, discussed with 

 him some of his ideas regarding cells in plants, which he had been studying 

 in his laboratory. Schwann had been making similar observations on 

 animals, and after the meal the two went to Schwann's laboratory, where 

 they came to the conclusion that cells are fundamentally alike in both 

 kingdoms. Schleiden's treatise on the subject, Beitrdge zur Phylogenesis, 

 appeared in 1838 and dealt mainly with the origin of cells. Robert Brown 

 had recently discovered the nucleus, and about it Schleiden built up his 

 theory of "free cell-formation," which was essentially as follows: In the 

 general cell contents or mother liquor (" cytoblastema ") there are formed, 

 by a process of condensation, certain small granules (later called "nu- 

 cleoli" by Schwann). Around these many other granules accumulate, 

 thus forming nuclei ("cytoblasts"). Then, "as soon as the cytoblasts 

 have attained their full size, a delicate transparent vesicle appears upon 

 their surface." This vesicle in each case enlarges and forms a new cell, 

 and, since it arise? upon the surface of the cytoblast (nucleus), "the 

 cytoblast can never lie free in the interior of the cell, but is always en- 

 closed [i.e., imbedded] in the cell wall . . . " Schleiden thus regarded 

 new cell-formation as endogenous ("cells within cells") rather than the 

 result of cell-division. With respect to the main proposition of the Cell 

 Theory he says in the opening paragraphs: " . . . every plant developed 

 in any higher degree, is an aggregate of fully individualized, independent, 

 separate beings, even the cells themselves. Each cell leads a double 

 life: an independent one, pertaining to its own development alone; 

 and another incidental, in so far as it has become an integral part of a 

 plant. It is, however, easy to perceive that the vital process of the in- 

 dividual cells must form the first, absolutely indispensable fundamental 

 basis, both as regards vegetable physiology and comparative physiology 

 in general; . . ." 



Schleiden shared the results of his observations, including his errors, 



