178 THE CIRCULATION 



here called lymph, and conveys nourishment to the cells ; the 

 latter being bathed constantly by the lymph, extract therefrom 

 what they require for nourishment, and excrete into it their 

 waste materials. The lymphatic system begins in irregular 

 spaces between the cells, which gradually unite to form small 

 Jymph capillaries,. which gradually increase and unite to form 

 larger and larger vessels, which finally end in the large thoracic 

 duct. This duct ascends through the abdomen and chest to 

 the root of the neck, where it is joined by lymphatics from the 

 left side of the head and the left upper extremity, and empties 

 itself into the left subclavian vein. 



51. The lymphatic vessels from the right side of the head and 

 neck, and the right upper extremity, form the right lymphatic 

 duct which terminates in the right subclavian vein. Thus the 

 lymph collected from the tissues of the entire body is mingled 

 with the venous blood a little before its arrival at the right side 

 of the heart. Along the course of the lymphatic vessels through- 

 out the body are found numerous glands, called lymphatic 

 glands, through which the lymph percolates in its flow toward 

 the heart. The function of these glands is not definitely 

 known, but they are supposed to produce the white globules 

 of the blood, as they contain numerous cells in structure 

 and appearance identical to them. The lymphatic vessels are 

 supplied with numerous valves, in structure like those of the 

 veins, and the flow of lymph through the lymphatic system is 

 dependent upon the same causes which govern the flow of 

 blood through the veins. 



52. Injuries to the Blood-vessels. It is important for us to 

 be able to discriminate between an artery and a vein, in the 

 case of a wound, and if we remember the physiology of the 

 circulation we may readily do so. For, as we have already 

 seen, hemorrhage from an artery is much more dangerous than 

 that from a vein. The latter tends to cease spontaneously 

 after a short time. The arterial blood flows away from the 

 heart with considerable force, in jets, and its color is bright 



51. Describe the right lymphatic duet. 



62. What is stated of the injuries to the blood-vessels ? 



