MUSCLE-TISSUE. 265 



muscles appear, replacing the striped muscles, which are present 

 in the two upper thirds ; the boundary line between the two is 

 not sharply marked, as the fibers of both varieties blend with 

 each other (Treitz). 



The pregnant uterus is constructed of numerous and large 

 muscle-fibers, also arranged in longitudinal, transverse, and 

 oblique bundles. The bioplasson in this situation is very abun- 

 dant, giving the spindles a coarsely granular, nearly homogene- 

 ous, appearance, without a distinct nucleus. Every large spindle 

 is composed of a number of smaller ones. The boundary line 

 between the latter is often marked at the periphery of the large 

 spindle only, or else a faint oblique trace of demarcation may be 

 observed within a large spindle. (See Fig. 110.) 



Blood- and Lymph-vessels are numerous in the smooth muscle- 

 tissue, producing an elongated, more or less rectangular, retic- 

 ulum. Larger blood- and lymph-vessels are found in the denser 

 formations of connective tissue between groups of bundles, 

 while the delicate perimysium surrounding the bundles contains 

 only capillaries. 



The nerves of smooth muscle bundles, after repeated plexi- 

 form ramifications, branch in the form of delicate axis fibrillae 

 in the cement-substance between the spindles (M. Lowit). Some 

 observers claim that the axis fibrillse enter the spindles and ter- 

 minate in the nucleolus (Frankenhauser), or pierce the nucleus 

 and the nucleolus, in order to again reach the plexus on the 

 opposite side of the spindle. Here, as well as in striated muscle, 

 a terminal nerve-hill may exist, as indicated in Fig. 109, though 

 its relations are not yet sufficiently studied. 



2. STRIPED MUSCLE. 



Striped muscle is composed of comparatively large fusiform 

 and sometimes blunt spindle-shaped fibers, which are separated 

 from each other by means of a delicate connective-tissue forma- 

 tion, and are held together in bundles by means of broader lay- 

 ers of the same tissue. Each bundle is composed of a varying 

 number of fibers. The fiber is built up by more or less regularly 

 arranged layers of sarcous elements, formations of bioplasson, 

 which are interconnected in all directions by delicate filaments 

 of bioplasson, while the meshes between the sarcous elements 

 contain a non-contractile, non-living fluid, which can be artifi- 

 cially pressed out of every muscle. 



