438 



LABORATORY MANUAL OF HUMAN ANATOMY 



they- are all derived phylogenetically from the sphincter of the 

 cloaca. (Vide Holl, Die Muskelen im Beckenausgange des Men- 

 schen; Merkel-Bonnet, Ergebnisse der Anatomie, xi., 1901.) 

 Study the form, position, origin, insertion, action, and innerva- 

 tion of each. 



(a) Superficial transverse muscle of perineum (M. transversus perinei 

 superficialis) . 



In the embryo and child this muscle is well developed and con- 

 stant in its relations. In the adult the muscle varies in size, 

 strength, and position; in the foetus muscle bands are found 

 connecting it to the M. sphincter ani externus and the M. ischio- 

 cavernosus, and it may be regarded as a connecting link between 

 anal musculature and the musculature of the urogenital region. 

 In the adult it seems to be underging retrogressive changes. 



FIG. 223. 



lig. sacrotuberosum _ . 



M. coccygeus 



M. sphincter an 

 ext. 



M. transversus perinei _ 

 superficialis 



^. Lig. sacrotuberosum 



M. obturator internus 



Acetabulum 



M. ischiocavernosus 



M. bulbocavernosus 



Corpus penis 



Permeal muscles of man. On the right side the anterior part of the lig. sacrotuberosum is removed 

 the M. obturator internus is divided, the M. levator ani is shown, but not labelled. (From Gegenbaur, 

 Lehrb. der Anat. des Mensch., Leipzig, 1899, 7 Aufl., Bd. ii. p. 197, Fig. 496.) 



(6) Ischiocavernous muscle (M. ischiocavernosus) (0. T. erector penis 

 muscle). 



According to Merkel, the tendon of this muscle fuses, as a 

 rule, with the lower and lateral surfaces of the fibrous tunic of 

 the corpora cavernosa. At times a tendinous slip is given off, 

 which fuses with a corresponding process from the opposite side, 

 on the dorsum of the penis, and thus forms a. loop about the 

 dorsal vein of the penis. These processes may be muscular. If 

 so, they are called the " compressor muscle of the dorsal vein of 

 the penis" (M. compressor venae dor sails penis}. 



