HIGHER TENSILE CONNECTING TISSUES 



are flattened out somewhat, but not drawn out as in the tendon. 

 These cells seem to have formed a second set of extremely minute 

 fibrils which lie between the large, heavy fibrils of elastic tissue and 

 at points appear to be attached to them. These loose fibrils appear 

 to be a lax connective tissue. 



The lower forms of animals show but few examples of specialized 

 ligaments, owing to the general distribution of the muscles and their 

 large areas of attachment. Also many of these forms have no skeleton, 

 and consequently the muscles work in masses of connective tissue and 

 in a series of opposed planes. 



The Crustacea have a 

 rigid exoskeleton or shell and 

 a series of powerful, quick- 

 acting muscles that require 

 firm attachment to the inside 

 of the shell. They are at- 

 tached by very short liga- 

 ments, as is described below. 

 No long ligaments exist, and 

 therefore when a muscle does 

 not reach, by some little dis- 

 tance, to its point of attach- 

 ment, an inwardly produced 

 process of that point, com- 

 posed of hypodermis and 

 cuticle, reaches in to meet 

 the muscle. These integu- 

 mental "ligaments" are char- 

 acteristic of the Crustacea 

 and may be seen by exam- 

 ining the muscle of a lob- 

 ster's great claw. 



A tissue, however, that 

 acts as a very short ligament 

 does exist in the lobster 

 wherever a muscle is attached 

 to the shell or to one of its 

 inside processes. It is not 

 connective tissue alone, how- 

 ever, that serves this pur- 

 pose. The simple, columnar 



epithelium cells that cover the outside of the body under the shell, 

 which they form, assume part of this duty and acquire strength to 



mus. c. 



FIG. 67. Portion of the new integument of a lob- 

 ster, Homarus. conn.t.n., connective-tissue nucleus; 

 bl.c., blood cells; mus.c., muscle cells. 



