ADDRESS. 17 



Function of Cells. 



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

 existing 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 pai-ts 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 

 recognised in the cells of the liver, kidney, and othe» organs the character- 

 istic secretion of each gland. The secretion was, he said, situated between 

 the nucleus and the cell wall. At tirst 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 recognised. 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 

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

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

 trated in tlie centre. Similar observations on the skin of the froe 

 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 papei' on the pigmentary system in the frog, pub- 

 lished in 18.58, Lord Lister demonstrated that the pigment granules 

 moved in the cell plasma, by forces resident within the cell itself, 

 acting under the influence of an external stimulant, and not by a 

 contractility of the wall. Under some conditions the pigment was 

 attracted to the centre of the cell, when the skin became pale ; under 

 other conditions the pigment was diffused throughout the body and the 

 branches of the cell, and gave to the skin a dark colour. It was also 

 experimentally shown that a potent influence over these movements 

 was exercised by the nervous system. 



The study of the cells of glands engaged in secretion, even when the 



1900. * c 



