16 CELL THEORY BEFORE 1860 GOODSIR. 



the chief stages in its progress, with a few connecting 

 observations. 



Several important changes were introduced into the ahove 

 theory hefore it became for a time established, in spite of these 

 changes, still as a cell theory. In 1841 Henle adopted the cell 

 theory of Schleiden and Schwann, but pointed out the multi- 

 plication of cells by division and budding. In the same year 

 Dr. Martin Barry showed the reproduction of cells by division 

 of the parent nucleus, and confirmed Schleiden in the im- 

 portance of the nuclei, as new cell-formers. But the first im- 

 portant contributions to the cell theory, after Schwann, were 

 the memoirs of J. Goodsir, in 1842 and 1846 ("Anatomical 

 Memoirs," vol. ii.), and they still remain probably the most im- 

 portant till the time of Dr. Beale. The first was on secreting 

 structures, and as growth and secretion are substantially the 

 same vital processes the theory of Schwann received elucida- 

 tion and development from another side, as it were. Since the 

 time of Malpighi, the secreting glands were known to be com- 

 posed essentially of tubes with blind extremities, but the 

 exact seat of the vital process of secretion was not agreed upon. 

 By Fletcher, and probably the majority of physiologists, it 

 was supposed to be the walls of the capillary vessels. Schwann 

 suggested it was in the epithelium of the mucous membrane 

 of the ducts, and Purkinje hypothetically placed it more 

 definitely in the nucleated epithelium, but did not verify that 

 hypothesis by observation. Goodsir brings together a number 

 and variety of observations on the secreting organs of animals 

 from the mollusca up to mammals, and finds a common cha- 

 racter running through them all, viz., that the specific secretion 

 is found inside the nucleated epithelial cells, between the 

 nucleus and the wall of the cell. The animals were selected 

 on account of the striking colour possessed by the secretion, 

 such as the Loligo sagittata, on account of its ink-bag ; the 

 Phallusia mdgaris, for the dark-brown fluid of its hepatic 

 organ ; the Janthina fragilis, for the purple fluid secreted by 

 the inner surface of its mantle, and which is the source of the 

 Tyrian dye, &c. In many cells the secretion is so transparent 

 and colourless, that ocular proof of its formation within the 



