SCIENCE-GOSSIP. 



251 



to further discoveries of a similar nature by 

 Schleiden. He showed that these nuclei were 

 found in the cells of many species of plants ; but 

 that only occurring, so far as he could observe, in 

 the young cells, he argued they had therefore some 

 near connection with the mysterious commencement 

 of the cell, and consequently must form a prominent 

 feature in vital development. To a certain point 

 Schleiden was correct, for the nuclei do act as 

 important factors in progressive growth, but they 

 do not affect the beginning of cell formation. How- 

 ever, by means of these observations on plant 

 structure the cell theory was first applied to animal 

 substances, and a great interest was centred in 

 the application of this theory, since it is in the 

 animal cell that the nuclei stand out most promi- 

 nently. We cannot, however, ignore the work 

 which had been done about this period by others 

 who endeavoured to show that the animal tissue 

 was built up of numerous minute elements ; but 

 these theories could not be developed further 

 because of the incorrect observations on which 

 they were based, so that any beneficial results 

 which might have been obtained would only have 

 been outweighed by errors. Purkinje ( 9 ), Miiller ( 10 ), 

 and Henle (") — all three had worked out theories 

 on the cell formation of animals and plants — en- 

 deavoured to show the correlation existing between 

 the different portions of the animal tissue and that 

 of the vegetable. It was not, however, until the 

 idea suggested itself to Schwann, in a conversation 

 he had with Schleiden on the merits of the cell 

 theory, that the resemblance between the cells of 

 the plant and animal tissue might be of impor- 

 tance in the development of the vital phenomena, 

 that anything feasible was arrived at. He at once 

 set on foot a series of experiments, and the results 

 of these experiments he published in his book 1 1, 

 which may be considered as the most valuable 

 work of the period. It was the means of extending 

 the knowledge of the microscopical structure of 

 the anatomy of animals, and notwithstanding the 

 difficulties in observation which had to be sub- 

 mitted to, the result of Schwann's researches was 

 to elevate animal anatomy to the same level as 

 that of plants. 



The cell is the true basis of knowledge, both 

 morphologically and physiologically, in zoology and 

 botany, and it must therefore be regarded as an 

 integral organism possessed of independent life. 

 Schwann made most important use of the nucleus 

 in demonstrating the animal cell, emphasising the 



rtini<en 

 .-«i«eh<-n '.• • rl»ndl«:be Cullur In 



vffilltr 



statement that it is the most characteristic and 

 least variable of the cell constituents. Whether 

 we examine a flower, section of a stalk, or fruit, or 

 extend our observation to the structures of bone, 

 skin, or flesh, the same truism manifests itself, and 

 we find these structures built up of cells aggre- 

 gated together. Various views have been enter- 

 tained as to the constitution of the cell or unit 

 and its real nature, but whatever view may 

 eventually be adopted as regards its nature and 

 structure, it must be acknowledged to be a 

 unit of independent function and existence. 

 Briicke ( 13 ) emphasises it as an elementary organ, 

 and the anatomist, Virchow ( u ) styles it the seat of 

 life, but Ha^kel ( 10 ) defines it as the " organic unit 

 of form of the lowest grade," and assumes this 

 definition to be the most accurate description of 

 this wonderful organism. It is functional, both 

 anatomically and physiologically, and is found 

 constituting one-celled plants — the Protesta — and 

 animals. The term, however, is not perhaps so 

 well chosen as to be free from some objection to 

 its general application ; but Schlieden adopted it 

 as the most comprehensive term to describe those 

 small organisms which in most plants, when made 

 in cross section, had in appearance great affinity to 

 the chambers of the honeycomb, being all massed 

 together, but separated by a wall or partition, and 

 filled with some kind of liquid or soft pulpy matter. 

 When this theory was applied to the animal world, 

 the same terms were adapted by Schwann as 

 sufficiently descriptive of a small sac closed, or 

 bladder filled with fluid, and surrounded by a solid 

 wall or outer covering. This was the general term 

 applied to describe those single structures which 

 are such important and prominent factors in the 

 progression of all animal and vegetable life. Yet, 

 however, some anatomists do not consider the 

 description to be an adequate conception of the 

 phenomenon of cell life, and regard the choice of 

 the term as misplaced, for it is argued that those 

 parts of the animal body which had hitherto 

 been denominated cells were on investigation 

 shown to be different, while the further investi- 

 gation was carried the plainer it became that the 

 nature of the cell must be " entirely differently 

 conceived." 



To meet this view the cell is now defined ( ll1 ) 

 as " a small solid, or semifluid— that is, neither solid 

 nor fluid — dense body, the chemical nature of which 

 is albuminous, and in which another roundish body, 

 generally more solid, and always albuminous, is 

 enclosed. An envelope or membrane may exist, 



■ 



: rxlrmldm " 



14 1 . . • \tln»- 



ht-r dl'r 



lUinmant li ihum dcr 



1 ]■ im nt.irorKanl»mcn wiener elu- 

 '.1, xllv. 2. Abtbi 

 I Cellulu 1 '.ulioloity 0'i based 011 I'hyalo- 



logici) sod !■' Ililology." Translated l>y Chanel, 



, vol 1. London, >M3. 

 1 Bvolotlon of Mao," vol l,p >.-, London, 



