130 



LOCOMOTION. 



[CHAP. vi. 



Fig. 35. 



of the rabbit, is represented in fig. 34. This was discovered, by 

 Henle. We have found this epithelium to rest immediately 

 on a continuous transparent basement membrane of excessive te- 

 nuity, apparently identical with that which supports the epithe- 

 lium of mucous membranes. Beneath this is a lamina of areolar 

 tissue, which constitutes the chief thickness of the membrane, 

 and confers on it its strength and elasticity. This areolar tissue 

 is traversed by a network of capillary vessels, the meshes of which 

 are large and of rather unequal size, and by lymphatics and ner- 

 vous filaments in varying number. It is of close texture, and 

 continuous with that laxer variety by which the membrane is 

 attached to the parts it lines. 



The most favourable position for examining the areolar tissue of 

 serous membrane, is the transparent part of the mesentery, or of 

 any of the dirplicatures of the peritoneum, in small animals. 



Here we observe the yellow 

 fibrous element assuming a very 

 beautiful arrangement (fig. 35). 

 Its filaments interlace and in- 

 osculate chiefly in a plane be- 

 neath the basement membrane, 

 in such a manner as to confer 

 equal elasticity in every direc- 

 tion. The intermediate space 

 is occupied by the white fibrous 

 element disposed in wavy 

 bands, variously intersecting, 

 and which become straight only 

 when the elastic threads are 



Yellow fibrous element of the areolar tissue of serous , , 



membrane. From the mesentery of the Rabbit, treated Stretched. 

 with acetic acid. Magnified 300 diameters. 7-17-7 7 - i n 



Physical and vital Proper- 

 ties. These are precisely those of areolar tissue : the elasticity of 

 the serous membranes is very considerable, owing to the admixture 

 of the yellow fibrous element in the layer which forms the chief 

 substance of the membrane. These tissues are entirely devoid of 

 vital contractility ; and their sensibility is low, except in a state of 

 acute inflammation. 



These membranes exhibit, in their inflamed state, a remarkable 

 tendency to throw out lymph on their interior, so as to cause 

 adhesion of their opposed surfaces. Hence a frequent result of in- 

 flammation of a serous membrane is the obliteration, to a greater or 

 less extent, of its cavity. Synovial membranes are not so prone 



