1 58 GENERAL ANATOMY. 



volume varies from that of a grain of millet to that of the dis- 

 tended abdomen; here we find them isolated, and there several 

 grouped together and communicating with each other; their 

 external surface is floculent, cellular, sometimes having laminae, 

 or even a fibrous layer; sometimes this surface is lined with a 

 natural membrane which they have encroached upon in sally- 

 ing towards a surface; their internal surface is smooth and 

 polished: the thickness varies, and is in general less in the 

 cysts of the organs, than in those of the free cellular tissue; it 

 is also greater or less in different parts of the same cyst; the 

 consistence varies from that of a barely concrete liquid, to that 

 of the serous and even of the fibrous tissue; it is the same with 

 their adhesions which are sometimes very close, and at others 

 seem to be a simple agglutination: there are no apparent ves- 

 sels on their free surface. 



The liquid they contain is not less various. At one time, 

 we find it a serum, either limpid or more or less thick like 

 albumen, variously coloured; at another it is fat, either fluid, 

 or in particles forming cholesterine; in some cases it is mucus 

 or a viscid substance, which, instead of coagulating by heat, 

 evaporates almost wholly, leaving but very little residuum; 

 in others it is a mixture of mucus and albumen, or a blackish 

 matter resembling chocolate, sometimes even pure blood; at 

 others hydatid worms; sometimes crystallized saline sub- 

 stances : a concrete substance has also been found there, re- 

 sembling caoutchouc. 



The cysts are in a state of repletion that may be compared 

 to the dropsies of the serous membranes : they are the seat, 

 however, of a continual secretion and absorption ; they disap- 

 pear in certain cases, persist in some, and continually increase 

 in others. 



Different theories have been proposed to explain the forma- 

 tion of cysts. Some authors regard them as membranes of a 

 new formation which are developed round an originally exist- 

 ing substance; others again, on the contrary, think they are 

 pre-existent to the matters they contain, whether they be form- 

 ed by the distended cellular tissue, or owe their production to 

 the dilated lymphatics. It is difficult to say, exactly, which of 



