280 



FASCI.E AND MUSCLES OF THE HORSE 



Fig. 271. — Cross-section of Tail of Horse. 

 1, 2, Branches of lateral coccygeal reaaels and nerve; 3, mid- 

 dle coccygeal artery; 4, sacro-coccygeus dorsalis; 4', sacro-coccy- 

 geus lateralis; 5, 5', iatertransveraales; 6, sacro-coccygeus ven- 

 tralis; 7, recto-coccygeus; 8, coccygeal fascia; 9, fibro-cartilage 

 between fourth and fifth coccygeal vertebrse. The veins are blaclt. 



Origin. — The pelvic surface of the sacro-sciatic hgament near the ischiatic spine. 

 Insertion. — The first four coccygeal vertebrae and the coccygeal fascia. 



Action. — Acting together, to de- 

 press (flex) the tail, compressing it 

 over the perineum; acting singly, 

 to depress and incline it to the 

 same side. 



Structure. — The origin of the 

 muscle is aponeurotic. Becoming 

 fleshy, its fibers pass upward and 

 backward and divide into two 

 layers. The lateral layer is at- 

 tached to the vertebrse, the medial 

 to the fascia; included between 

 the two lie the intertransversales. 

 When the tail is raised, the ventral 

 edges of the muscles produce a dis- 

 tinct ridge at either side of the anus. 

 Relations. — Laterally, the 

 sacro-sciatic ligament and the semi- 

 membranosus ; medially, the rectum 

 and the sacro-coccygeus ventralis 

 muscle. The internal pudic artery 

 crosses the origin of the muscle. 

 2. Sacro-coccygeus dorsalis (M. sacrococcygeus dorsalis medialis).i — This 

 muscle lies along the dorso-median aspect of the tail, in contact with its fellow. 



Origin. — The last three sac- 

 ral spines and some of the coccy- 

 geal spines. 



Insertion. — The dorsal sur- 

 face of the coccygeal vertebrse. 



Action. — Acting together, to 

 elevate (extend) the tail; acting 

 singly, to elevate and incline it 

 laterally. 



Structure. — The muscle has 

 a strong rounded belly. It is in- 

 serted by means of short tendons 

 which fuse with those of the next 

 muscle. 



Relations. — Superficially, the 

 coccygeal fascia; medially, its 

 fellow; laterally, the sacro-coccy- 

 geus lateralis; deeplj^, the verte- 

 brae. 



.3. Sacro-coccygeus lateralis 

 (M. sacro-coccygeus dorsalis later- 

 alis).- — This muscle lies immedi- 

 ately lateral to the preceding. 



Origin. — The sides of the ,:-„,„,, 



iiG. 272. — Muscles of Pekineum of Horse. 

 a. Coccygeus; h, retractor ani; c, c', sphincter ani crternusr 

 d, recto-coccygeus; e, sacro-coccygeus ventralis lateralis; /, retrac- 

 tor penis; g, bulbo-cavernosus; h, ischio-cavernosus; i, internal 

 pudic artery; k, anus; I, penis. (After EUenberger-Baum, Top. 

 Anat. d. Pferdes.) 



