320 INTEGUMENTS. 



titious arrangement upon being drawn or inflated. For ex- 

 ample, if one separates two muscles for a short distance, the 

 cellular substance between them becomes unequal and furrowed 

 without losing its cohesion; but if they be farther separated, 

 filaments and cylindrical columns are produced. If the trac- 

 tion be then suspended, and the muscles replaced, the filaments 

 shorten, and are finally united into a consistent mass whose 

 parts all adhere together.* 



While such tractions are going on, it most frequently hap- 

 pens that air is insinuated into the cellular substance, from which 

 corrres the appearance of small cells and vesicles : upon the es- 

 cape of this air, the primitive state of cohesion is restored, and 

 upon a renewal of the traction, cells of a different shape, size, 

 and appearance arise. Again, if air be so introduced, one may 

 push it in any direction, separate its globules, collect them again, 

 and into larger masses; vary their shape, and, in fine, by such 

 means mould the supposed cells into an infinity of forms. From 

 these considerations, the inference is plain, that when cellular 

 substance is drawn it must yield itself into filaments; when in- 

 flated, as the air acts in every direction, its supposed lamellae 

 must be separated and assume a cellular shape; and, by the ap- 

 plication of both forces at once, it may be caused to assume 

 both a cellular and a filamentous appearance. Upon the whole, 

 Meckel conceives that the term Mucous Tissue, adopted by 

 Bordeu, is much more exact than the one of Cellular Tissue, 

 now most generally used. 



Notwithstanding the perfect continuity of the mucous or cel- 

 lular substance throughout the body, anatomists for the ease of 

 description have divided it into External and Internal. 



The External Cellular Substance (Textus Cellulosus Inter- 

 mediuSj sen laxus) has the general extent and shape of the body 

 and of its organs, so that if it were possible to extricate the lat- 

 ter from their envelope, it would present a chamber for the 

 lodgement of each part. But the walls of these chambers 

 would not all be of the same thickness, as the quantity of cel- 

 lular substance varies. In the cranium and spinal cavity there 

 is very little of it: on the surface of the head and in the orbits 

 more: about the trunk, both internally and externally, it is abun- 

 dant; in the extremities still more so, where it penetrates between 

 * J. F. Meckel, loc. cit. 



