494 LECTURE XIX. 



whilst mucus- and pus-corpuscles under all circumstances 

 remain round. Even from this circumstance may be 

 derived an explanation of the fact that, whilst the epithe- 

 lial cells, which cover, and are in close apposition to, one 

 another, acquire a certain firmness of cohesion, mucus- 

 and pus-corpuscles which lie but loosely one against the 

 other, and are of a spherical shape, retain a great degree 

 of mobility and are easily displaced. 



It has been said before now that mucus-corpuscles are 

 nothing more than young epithelium ; another step and 

 pus-corpuscles would be nothing more than young mucus- 

 corpuscles. This is a somewhat erroneous notion. It 

 cannot be maintained that a cell, which up to the point 

 when it becomes a so-called mucus corpuscle has pre- 

 served its form as a spherical body, is still in a condition 

 to assume the typical form of the epithelium, which ought 

 to exist in the part ; and just as little can it be said that 

 a pus-corpuscle, after it has developed itself in the regu- 

 lar manner, is capable of again entering upon a course of 

 development calculated to produce a relatively perma- 

 nent element of the body. The cells, in which the deve- 

 lopment of epithelial, mucus-, and pus-cells originates, 

 are young forms, but they are not pus-corpuscles. In 

 pus every new cell at a very early period sets about 

 dividing its nucleus ; after a short time the division of 

 the nucleus reaches a high pitch, without any further 

 growth on the part of the cell. In mucus the cells are 

 wont merely to grow, and in some instances to become 

 very large, but they do not pass certain limits, and above 

 all they do not assume any typical form. In epithelium, 

 on the contrary, the elements begin even at a very early 

 period, to assume their particular form, for u what is to 

 become a hook^ right early gets a crook." The very 

 youngest elements however, which are found in patholo- 

 gical conditions, cannot be called epithelial cells, or at 



