The _Gemelli_ or Twin Muscles arise from two small Knobs in the hinder-part of the _Ischion_ and insinuate themselves into a small Cavity in the Neck of the great _Trochanter_. The Circular Motion of the Thigh is performed by the means of two Muscles, named the _Obturatores Externi_ and _Interni_. The _Obturator Internus_ springs from the inner Circumference of the Oval Hole of the _Ischion_ and its _Tendons_ passing between the two _Gemelli_ are inserted in a small Cavity at the Root of the great _Trochanter_ or _Rotator_. The _Obturator Externus_ ariseth from the outward Circumference of the same Hole of one _Ischion_, and is terminated in the side of the other near the great _Trochanter_. _What are the Motions of the Leg, and what are its Muscles?_ The Leg is mov'd four several ways, that is to say, it is bent, extended, and drawn inward and outward, by the means of eleven Muscles _viz._ three _Flexors_, four _Extensors_, two _Adductors_ and two _Abductors_. The three _Flexors_ of the Leg are the _Biceps_, the _Semi-nervosus_, and the _Semi-membranosus_. The _Biceps_ hath two Heads, the longer whereof cometh out of the bottom of the Prominence {51} of the _Ischion_, and the other from the middle and exterior part of the _Femur_, and is terminated in the outward and upper part of the _Epiphysis_ of the _Perone_ or _Fibula_. The _Semi-nervosus_ hath its Origine in the Knob of the _Ischion_, and is join'd backward to the top of the _Epiphysis_ of the _Tibia_. These three Muscles are plac'd in the back-part of the Thigh below the Buttocks. The four _Extensors_ of the Leg are the _Rectus_, the _Vastus Internus_, the _Vastus Externus_, and the _Crureus_. The _Rectus_ or streight Muscle of the Leg takes its rise from the fore-part and the bottom of the _Ilion_, and descends in a right Line: It covers with its _Tendon_, which is common to the three following, the whole Knee-Pan, and adheres to the top of the _Tibia_, on the fore-part. The _Vastus Internus_, being situated on the inside of the Thigh, hath its beginning in the top of the Thigh inwardly, and a little below the lesser _Trochanter_ or _Rotator_: Afterward it is ty'd to the _Tibia_ by a large _Tendon_, common thereto with the preceeding. The _Vastus Externus_ is plac'd on the outside of the Thigh, springing from the top and the fore-part of the _Femur_, being united by the same _Tendon_ with the two preceeding. The _Crureus_ proceeds from the top, and the fore-part of the Thigh-Bone, between the two _Trochanters_; then covering the whole Bone, it is also fasten'd to the Leg-Bone with the three preceeding Muscles, after having cover'd the Knee-Pan with their common {52} _Tendon_, which serves likewise as a Ligament to the Knee. The two _Adductors_ of the Leg are the _Sartorius_ and the _Gracilis_.