Note dorsally of the trachea a long tube passing through the diaphragm and connecting the mouth with the stomach. What is this tube? Note the _Eustachian tubes_ extending from the mouth to the ears. The median part of the roof of the mouth is the _palate_, hard in front, soft behind. A pair of small bodies at the sides of the soft palate near its hinder end are the _tonsils_. At the posterior angle of the lower jaw are glandular bodies, the _sub-maxillary glands_, which lead by a short _duct_ anteriorly to open on the floor of the mouth. On the sides of the neck just below the ears are pink or yellowish bodies, the _parotid glands_, opening anteriorly in the sides of the mouth-cavity. These two sets of glands are collectively known as the _salivary glands_, the function of which is to secrete the saliva. Push apart the sub-maxillary glands and note below them overlying the trachea on either side two dark-red lobes connected by a band of tissue. These constitute the _thyroid gland_, another of the so-called ductless glands. Within the thoracic cavity anterior to the heart note a mass of pinkish tissue, the _thymus gland_. Observe the large _masseter muscles_, which cover the jaws. What is their function? On either side of the neck lies a large blood-vessel, the _external jugular vein_, which collects blood from the head and carries it down to the heart. Note the large _pectoral muscles_ which cover the breast and extend out into the arms, and which are so strong and highly developed in the sparrow. The head is supported by large muscles which run down the back of the neck to the ribs. Others are attached to the ribs, which they raise and lower. These movements, together with the contraction of the diaphragm, cause the expansion and contraction of the thoracic cavity whereby the lungs are regularly filled and emptied. Note that the abdomen is covered by a double layer of muscular tissue, the outer part made up of the _external oblique muscles_, the inner by the _internal oblique muscles_. [Illustration: FIG. 148.--Diagram of the circulation of the blood in a mammal; _a_, auricles; _l_, lung; _lv_, liver; _p_, portal vein bringing blood from the intestine; _v_, ventricles; the arrows show the direction of the current; the shaded vessels carry venous blood, the others arterial blood. (From Kingsley.)]