skin with scissors along the middle line, throughout the whole length of the body. Pin back the skin on each side, and make a drawing showing:—

(a) The muscles:

(i) Two pectoralis muscles passing from the base of the arm, the one to the middle line of the body, and the other over the abdominal region to the posterior part of the body. Cut through this latter muscle at its anterior end, and fold it backwards to expose the underlying brachial vein.

(ii) The rectus-abdominis muscles passing along the mid-ventral line of the body, with the white line (linea alba) in the centre.

(iii) The deltoid muscle to the arm.

(iv) The mylo-hyoid muscle, on the underside of the mouth region.

(v) The obliquus-externus muscle, lying under the second pectoralis muscle noted above.

(b) The cutaneous and the muscular veins, lying under the pectoralis muscle, and arising independently from the subclavian vein. They supply the skin and muscles in the region of the arm. There is a second cutaneous vein arising from the abdominal vein and extending on to the skin of the abdomen. Two other small cutaneous veins are seen on the skin of the leg, and another on the skin under the mouth.

[In the Frog a single musculo-cutaneous vein is seen lying under the pectoralis muscle and extends on to the skin.]

(c) The abdominal vein, partly visible through the wall of the body, in the centre of the rectus-abdominis muscle.

(d) The brachial vein going to the arm, near which may often be seen the white brachial nerve. Endeavour to trace the point of origin of the brachial, muscular, and cutaneous veins (or the brachial and musculo-cutaneous veins in the Frog) as shown in the figures.

Fig. 3.—Muscular System and Vascular System (part) of Xenopus and Rana.

2. Make an incision in the body wall, slightly to the right side of the abdominal vein, which may now be seen clearly on the inner side of the body wall. Carefully detach this vein from the abdominal wall.

Second Day.

Skeletal System (Part).

1. Remove the pectoralis muscles covering the body between the arms to show the bones of the central part of the shoulder girdle and sternum, viz.:—

(a) The thick coracoids.

(b) The more slender clavicles anterior to them, both extending from the base of the arm on each side towards the centre of the body.

(c) The sternum, consisting of a median row of cartilages which are believed to be derived from the shoulder girdle. It does not, therefore, correspond to, or is not homologous with, the sternum of the Pigeon or the Rabbit, which is derived from the ribs. The sternum consists of the following parts:

(i) The two epicoracoids consisting of cartilage.

(ii) The metasternum which is broad and consists of cartilage only.

Fig. 4.—Pectoral Girdle of Xenopus and Rana.

[In the Frog the sternum is composed of the following parts:—

(i) The omosternum consisting of two parts, an anterior cartilaginous part (sometimes called the omosternum) and a posterior bony part (sometimes called the episternum).

(ii) The two epicoracoids consisting of cartilage.

(iii) The metasternum consisting of two parts, an anterior bony part (sometimes called the sternum) and a posterior cartilaginous part (sometimes called the xiphisternum).]

Make a sketch of the pectoral girdle.

2. Cut through the coracoids and clavicles on each side, close to the base of the arm, and carefully remove this part of the pectoral girdle and sternum so as to show the heart lying underneath.

Fig. 5.—Dissection of Xenopus and Rana to show the Alimentary System, etc.

Alimentary System.

Make a sketch showing:—The heart, lungs, liver, gall bladder and bile duct going to the duodenum, exposed parts of the stomach, duodenum, small intestine (or ileum), large intestine, urinary bladder, pancreas, and spleen.

Third Day.

Vascular System (continued).

A. Venous System.

1. Note:—

(a) The heart lying in the thin pericardium, the two auricles, the single ventricle, the truncus arteriosus which divides into two branches.

Remove the pericardium from the heart, and tilt the apex of the heart forwards, noting the sinus venosus into which the right and the left superior venæ cavæ (or precavals) and the single inferior vena cava (or postcaval) open.

(b) The veins passing from each side of the sinus venosus. Each superior vena cava is joined by the following branches:—

(i) The external jugular vein from the region of the tongue and the mandible.

(ii) The internal jugular vein from the head and a thick subscapular vein from the shoulder. These veins join the superior vena cava independently of each other so that there is no innominate vein as in the Frog.

(iii) The subclavian vein, made up of a brachial vein from the arm, a cutaneous vein from the skin, and a muscular vein from the abdominal muscles. The cutaneous and the muscular veins are separate veins so that there is no single musculo-cutaneous vein.

[In the Frog the superior vena cava is joined by the following branches:—

(i) The external jugular vein, formed by the union of a lingual vein from the tongue and a mandibular vein from the margin of the lower jaw.

(ii) The internal jugular vein from the head and the subscapular vein from the back of the arm and shoulder, both joining the superior vena cava by a common vein, the innominate.

(iii) The subclavian vein, formed by the brachial vein from the fore-limb and a musculo-cutaneous vein from the muscles of the body and from the skin.]

(c) The hypoglossal and the glossopharyngeal nerves, both running alongside of the lingual artery.

Make an enlarged drawing showing the above parts (a) and (b).

2. Note the inferior vena cava, receiving the renal veins from the kidneys, the hepatic veins from the liver, and opening into the sinus venosus.

3. Trace back the abdominal vein, and note that it is formed by the union of the two pelvic veins, which pass along