OF THE INTERIOR MUSCLES. 439 



705. The cellular tissue of the interior muscles is not so 

 abundant, but is more compact than that of the other muscles. 

 Fibrous or ligamentous tissue is only found in the heart, where 

 it forms rings for the orifices of the ventricles, cords or ten- 

 dons for the fleshy columns of these cavities, aponeurotic ex- 

 pansions which constitute in a great measure thetricuspid and 

 bicuspid valves of the auriculo-ventricular orifices, and cords 

 in the borders of the semi-lunar valves of the arterial orifices. 

 Bichat, who only speaks of the tendinous cords of the fleshy 

 columns, had before indicated that tbere exists differences be- 

 tween them and the tendons. In the other parts nothing is 

 found analogous to the ligamentous tissue, except the submu- 

 cus fibro-cellular tissue, to whif h are attached the subjacent 

 muscular fibres. 



The interior muscles appear to possess more blood-vessels 

 than the exterior. M. Ribes, however, asserts the contrary. 

 The greater part of the nerves of these muscles, which how- 

 ever are not abundant, belong to the great sympathetic; seve- 

 ral are furnished by the pneumo-gastric, and some few by other 

 nerves of the spinal marrow. 



706. The irritability of the interior muscles presents the 

 same phenomena as that of the other muscles, except the 

 fibrillary agitation, which has only been observed to exist in 

 the heart. 



The internal muscles possess less irritability than the exter- 

 nal, depending on nervous influence. 



Mechanical irritation is much more efficacious than galvanic 

 action in determining their contractions. Galvanic irritation 

 acts but slightly on them through the medium of the nerves. 

 Nevertheless, the cardiac nerves and the heart being compre- 

 hended in a galvanic circle, the continued action of this agent 

 determines movements in the organ. 



The irritability or susceptibility of contraction of the inte- 

 rior muscles, is the more remarkable, from its being materially 

 excited by local agents, which act on the fibre through the 

 medium of the membrane that covers it; at other times the 

 cause acts by sympathy: thus the titillation of the throat, the 

 presence of a bougie in the urethra, of a suppository in the 

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