34 POPULAR SCIENCE MONTHLY. 



ADDEESS OF THE PRESIDENT BEFORE THE BRITISH ASSO- 

 CIATION FOR THE ADVANCEMENT OF SCIENCE. 



By Sir WILLIAM TURNER, F. R. S. 



II. 



FUNCTION OF CELLS. 



IT has already been stated that, when new cells arise within pre-exist- 

 ing cells, division of the nucleus is associated with cleavage of the 

 cell plasm, so that it participates in the process of new cell-formation. 

 Undoubtedly, however, its role is not limited to this function. It also 

 plays an important part in secretion, nutrition and the special functions 

 discharged by the cells in the tissues and organs of which they form 

 morphological elements. 



Between 1838 and 1842 observations were made which showed that 

 cells were constituent parts of secreting glands and mucous membranes 

 {Schwann, Henle). In 1842 John Goodsir communicated to the Royal 

 Society of Edinburgh a memoir on secreting structures, in which he 

 established the principle that cells are the ultimate secreting agents; he 

 recognized in the cells of the liver, kidney and other organs the char- 

 acteristic secretion of each gland. The secretion was, he said, situated 

 between the nucleus and the cell wall. At first he thought that, as the 

 nucleus was the reproductive organ of the cell, the secretion was formed 

 in the interior of the cell by the agency of the cell wall; but three years 

 later he regarded it as a product of the nucleus. The study of the 

 process of spermatogenesis by his brother, Harry Goodsir, in which the 

 head of the spermatozoon was found to correspond with the nucleus of 

 the cell in which the spermatozoon arose, gave support to the view that 

 the nucleus played an important part in the genesis of the characteristic 

 product of the gland cell. 



The physiological activity of the cell plasm and its complex chemical 

 constitution soon after began to be recognized. Some years before Max 

 Schultze had published his memoirs on the characters of protoplasm, 

 Briicke had shown that the well-known changes in tint in the skin of the 

 chameleon were due to pigment granules situated in cells in the skin 

 which were sometimes diffused throughout the cells, at others concen- 

 trated in the center. Similar observations on the skin of the frog 

 were made in 1854 by von Wittich and Harless. The movements were 

 regarded as due to contraction of the cell wall on its contents. In a 

 most interesting paper on the pigmentary system in the frog, pub- 



