488 LECTURE XXI. 



obtain quite corresponding results. Thus in place of the above clear sub- 

 stance, little granules are noticed which represent the secretion material 

 produced by the cells. During rest these granules are being formed con- 

 stantly to be given off during activity. There has been a great deal of 

 discussion as to whether, in the secretion of the glands, the cells themselves 

 are destroyed, or whether it is to be assumed that the cell, as such, retains 

 its protoplasm and nucleus intact, and merely gives up the specific secre- 

 tion produced by it. According to all known observations, the latter 

 conception appears to be the correct one, for if the cells of the gland them- 

 selves should undergo breaking down, then there should be considerable 

 evidence in the active gland of a renewal of cell material. As a matter 

 of fact, there is but little sign of any such cell division taking place. 



The cells of the various glands in the animal organism do not, to be sure, 

 show any marked difference from the cells of the other tissues. We 

 know that all sorts of different cells are constantly producing definite 

 products which take part in metabolism and in the exercise of particular 

 functions. We know, for example, that many cells give up ferments, 

 while others produce compounds of simple constitution; for example, the 

 cells of the suprarenal bodies produce adrenalin, and those of the intestine 

 form secretin. The formation of such products as an immediate con- 

 sequence of the activity of the cells escapes our observation only because 

 the amount formed is so small, and partly, as is the case with the 

 digestive ferments, because it is not these alone that are given up 

 by the cells, but there is a much larger amount of other material set free 

 simultaneously. 



We may consider the formation of the secretion by the gland-cells in the 

 same light, and trace it to the activity of the cells, and in a narrower sense 

 to the protoplasm and cell-nuclei. We do not wish to speak in order 

 to avoid misconceptions of a transformation of protoplasm into secretion, 

 as is often done, but rather of the production of the latter by cell activity. 

 We must remember that the gland-cells are constantly being supplied with 

 new material by the blood, from which the secretion can be formed. This 

 is taken up according as the cell requires such material, and by means of 

 complicated processes the cell manufactures the secretion from it. The 

 protoplasm itself remains behind in the cell together with the nucleus; 

 both are preserved for a new formation of secretion. If we were to 

 assume that the cells themselves were passing over into the secretion, it 

 would be much more difficult to explain the process. There is no doubt 

 that ferments play an important part in the formation of this secretion. 

 Thus the cells of the gland have to break down to some extent the protein 

 substance in the serum in order to construct the mucin which is contained 

 in the secretion. The fact that 'evidently quite extensive transformations 

 take place is shown by the fact that mucin contains a large amount of 



