146 MUSCULAR SYSTEM. [sect. 80. 



agree in all essential points of intimate structure. They consist of 

 connective tissue, which is characterised by the parallel course and 

 firm union of its elements, and its poverty in elastic fibres. The 

 elements of the connective tissue, the fibrils, can be easily seen in 

 fresh tendons, as well as in transverse sections of dried specimens, 

 where, as in other parts of the body, they are very fine. In funi- 

 cular tendons, they have a beautiful undulating course, parallel to 

 the long axis of the tendon ; and, in the fresh condition, cohere 

 so firmly, that the primitive bundles are with difficulty demon- 

 strated. But such fasciculi, 0-006'" to 0-008'" broad, and of 

 rounded polygonal form, do actually exist, as may be seen in 

 transverse sections of dried tendons, particularly after the addition 

 of alkalies. In the natural condition, they are so intimately 

 united with each other, that they cannot be isolated. On the 

 other hand, secondary and tertiary bundles are very distinct even 

 in fresh tendons. Thin partitions of loose connective tissue ex- 

 tend through the tendinous tissue, and, being all connected with 

 each other into a continuous system of parallel tubes, separate 

 the tendinous fasciculi into numerous larger and smaller groups. 

 Secondary bundles, mostly of a polygonal, but also of a rounded 

 or elongated form, and of 0-03'" to 0-05'" in diameter, may be 

 very clearly distinguished; also tertiary bundles with polygonal 

 contours of o*i'" to 0-5'" and more in thickness, and bounded by 

 somewhat thicker partitions. For the most part, also, there are 

 still larger divisions, which are composed of numerous tertiary 

 bundles, and which, firmly connected in very various numbers and 

 groups, and surrounded by a common envelope of lax connective 

 tissue, constitute the tendons themselves. 



The aponeuroses have either the same composition as the proper 

 tendons, and consist of several layers of parallel secondary bundles, 

 disposed in the same plane, or they more resemble the fibrous 

 membranes, and exhibit primary and secondary bundles decussating 

 in two or more directions (abdominal muscles, diaphragm). 



In the secondary bundles of all tendons, there are fine elastic 

 fibres in various stages of development; sometimes as rows of 

 narrow, spindle-shaped cells, connected by slender prolongations ; 

 sometimes as fully-developed fibres of uniform breadth, or as iso- 

 lated fusiform cells. The arrangement of these elements is every- 

 where the same ; they run at regular distances parallel to and 

 between the tendinous fasciculi ; so that in transverse sections of 

 the tendons the dark ends of the elastic fibres are seen distributed 

 over the whole area, at distances of 0-007'" to 0-008'". Besides 



