MODE OF ORIGIN OF CELLS. 39 



It is different with connective tissue. It cannot be doubted 

 but that here some of the cells that migrate into it proceed 

 from the blood ; and the question must necessarily remain open, 

 whether the connective tissue in those places where it maintains 

 its ordinary local relations, is not usually regenerated by this 

 means. W. Joung has expressed himself strongly in favour 

 of this as being the mode of formation in the oedematous 

 scrotum. 



Our knowledge of the mode in which nerves and muscles are 

 regenerated in the healthy organism is too limited to permit us 

 to enter into any discussion respecting them. The main point of 

 the question is connected with the growth of the gland cells, 

 the epithelia, and the rete malpighii. Is the opinion justified, 

 that the important discovery of Henle of the spontaneous 

 growth of the rete mucosum can be shaken ? 



The development of epithelia from the cells of the connec- 

 tive tissue has already been maintained by many, as by 

 Burkhardt, by Yirchow, and by Forster. Very recently Pagen- 

 stecher* has stated that they may proceed from exudation 

 corpuscles, and Biesiadecki says specifically that they come 

 from colourless blood corpuscles. Two facts ascertained by the 

 application of novel modes of investigation may lead to a 

 decision on this point. The first is the presence of migrating 

 cells between the epithelial cells (Recklinghausen), and the 

 second the circumstance that after the injection of finely 

 granular colouring matter into the blood, it is also met with 

 within the epithelial cells. The last is not a fact of much im- 

 portance, since particles of colouring matter can be floated to 

 whatever part a current of nutritive matter may set. The 

 presence of migratory cells is a more important circumstance, 

 but is likewise not very weighty. No one has hitherto observed 

 that the migrating cells become changed into epithelial cells ; it 

 is not really derogatory to us to say that we are still ignorant of 

 the significance of the migrating cells, and that we do not know 

 what becomes of them. Were any one to maintain that the 

 migrating cells are conjugation organisms, no stronger objec- 



* Wiener Sitzungsberichte, 1868. 



