Vital Physics. 7 



On the other hand the pure mechanical and physical use 



of a tissue determines in all cases ihe metamorphic differen- 



% 

 tiation to be serous, whether that membrane be hard or 



soft, continuous or segmentary. 



In the order of the animal economy, or in the extension 

 of complexity, from low to high degrees of organization, the 

 principle of the tripartite membrane is sustained, the 

 number of membranes increasing as the organization is 

 higher and more complex. 



Thus the lowest forms, as Porifera, have but one tri- 

 partite membrane. I. A silicon coat. 2. A very low 

 sarcode or jelly. 3. An undetected tissue existing in the 

 jelly, which gives the animal the power of alternately 

 relaxing and contracting, whereby water, at short intervals, 

 is propelled from pores extending from the internal mass to 

 the surface of the soft body. 



Man and mammalia are supposed to have ten or eleven 

 distinct and special tripartite membranes. 



1. The gastro-intestinal membrane (including serous, 

 mucous and muscular membranes ; and so of all the rest). 



2. The broncho-pleural membrane. 



3. The genito-urinary membrane. 



4. The mammary membrane. 



5. The vascular membrane. 



6. The lacto-lymphatic membrane. 



7. The ganglionic membrane. 



8. The loco-motive membrane. 



