144 ANATOMY FOE NURSES. [Chap. XIL 



blood. The lymph corpuscles, usually called leucocytes, agree 

 in their characters with the white corpuscles of the blood. 

 They vary in number in different parts, being more numerous 

 in the lymph which has passed through the lymphatic glands 

 than in that which enters these bodies, thus indicating the lym- 

 phatic glands as a source of these corpuscles. 



The chyle in the lacteals during digestion has a white aspect 

 dependent upon the fatty particles absorbed from the food, and 

 suspended in it like oil globules in milk. After fasting the 

 lacteals contain lymph which differs very little from the lymph 

 found in the ordinary lymphatics. 



The lymph, broadly speaking, is blood minus its red corpuscles. 

 The chyle is lymph plus a very large quantity of minutely 

 divided fat. 



Movements of the lymph. — The onward progress of the lymph 

 from the tissues to the veins is maintained chiefly by three 

 things. (1) The difference of the pressure upon the lymph in 

 the tissues, and the pressure in the large veins of the neck. As 

 we have already seen in our last chapter the pressure exerted 

 upon the blood in the capillaries is greater than that exerted 

 upon the blood in the veins. This pressure in the smaller blood- 

 vessels is communicated through the blood-plasma to the lymph, 

 and thus, though the lymph is not subjected to the same amount 

 of pressure as the blood in the capillaries, it still stands at a 

 higher pressure than the blood in the veins. We may consider 

 the lymphatics to form a system of vessels leading from a region 

 of higher pressure, viz. the lymph-spaces of the tissues, to a 

 region of lower pressure, viz. the interior of the large veins of 

 the neck. (2) On account of the numerous valves in the 

 lymphatics every pressure upon the tissues in which they lie 

 will, by compressing the vessels, cause an outward flow of their 

 contents. Active muscular exercise and the manipulation of 

 the tissues, as practised in massage, markedly affect the lymph 

 flow. (3) During each inspiration the pressure on the thoracic 

 duct is less than on the lymphatics outside the thorax, and the 

 lymph is accordingly "sucked" into the duct. During the 

 succeeding expiration the pressure on the thoracic duct is in- 

 creased, and some of its contents, prevented by the valve from 

 escaping below, are pressed out into the veins. 



The lymph in the various lymph-spaces of the body varies in 



