MUCUS. 127 



four, or five nucleoli, the usual number being two or three ; 

 the investing membrane at the same time under its influence 

 loses its granular aspect, and appears transparent and smooth. 

 (See Plate XL fig. 5.) 



The formation of these nucleoli may be thus explained : 

 The effect of acetic acid is to contract the entire corpuscle; on 

 the nucleus, however, it would appear to operate with such 

 force as to occasion a complete division of its substance. 



The divided nucleus has been observed by many observers 

 in the pus globule, but its occurrence in the mucous cor- 

 puscle has not been generally noticed ; this division of the 

 nucleus has been considered to constitute an exception to the 

 law of the development of a cell around a single nucleus ; 

 whether it ought to be so regarded is doubtful, seeing that 

 these multiplied nuclei are usually the result of the operation 

 of a powerful re-agent, and are but rarely visible, unless as 

 the consequence of the application of some re-agent. 



Mr. .Wharton Jones has endeavoured to meet this conceived 

 exception, by supposing that the nucleoli are all enclosed 

 within the membrane of the nucleus. I have myself, how- 

 ever, failed to detect the existence of any envelope surround- 

 ing the nucleoli. 



Form. The form of the mucous corpuscle, although usually 

 spherical, is subject to considerable variety, this depending 

 frequently upon the density of the fluid in which it is im- 

 mersed, but occasionally also upon the amount of pressure to 

 which it may be subjected. 



Thus, in fluid which is very dense, the operation of exos- 

 tosis is set up between the corpuscle and the fluid medium 

 which surrounds it, whereby a portion of its contents passes 

 into that medium, as a consequence of which its investing 

 membrane collapses and exhibits a variety of forms. (See 

 Plate XL fig. 2.) 



Corpuscles thus affected nevertheless retain the power of 

 re-assuming the form which properly belongs to them when 

 they are immersed in water or any other liquid, the density 

 of which is less than that of the fluid contained within the 

 cavity of the corpuscle itself. (See Plate XL Jig. 3.) 



