11 LYMPHATIC GLANDS 91 



very firmly fixed in this network as they are in that of 

 the glandular substance, and may be readily washed out 

 by shaking a thin slice of the gland in water. 



The lymphatic vessels which bring lymph to the gland 

 open directly into the channel of the lymph-sinus, and 

 those vessels which gather up the lymph to carry it away 

 from the gland open out of the lymph-sinuses. The arteries 

 supplying blood to the gland pass along the trabeculae. 

 cross the lymph-sinus, enter the glandular substance, and 

 break up into a network of capillaries from which the 

 blood is collected and carried away by small veins. 



The leucoc}i:es which crowd the glandular substance 

 present under the microscope appearances which leave no 

 doul)t that they are undergoing rapid and probably large 

 increase in numbers. But since the size of each gland is 

 ordinarily constant, a continual removal of the newly 

 formed leucocytes must be taking place. This view is 

 borne out by the observation that leucocytes are more 

 numerous in the lymph coming from a gland than in that 

 which flows to it. The removal takes place by a discharge 

 of leucocj'tes from the glandular substance into the meshes 

 of the neighbouring lymph-sinus, whence they are then 

 washed away in the current of lymph which is always 

 slowly flowing through the sinuses. In this way the 

 lymphatic glands provide a constant supply of leucocytes 

 which are passed ultimately into the blood and become 

 those white or colourless corpuscles with which we shall 

 have to deal in the next Lesson. 



The lymphatic glands have another very important 

 function. Bacteria which reach tliem iu the lymph from 

 some infected region are retained and destroyed in them. 

 Otherwise these bacteria would be poured with the lymph 

 into the blood and would infect the whole body. 



4. Causes which lead to the Movements of Lymph. 

 — Throughout the preceding description of the lymphatic 

 system we have spoken of the lymph as flowing along a 

 series of passages, from their origin in the tissues to the 

 point where they become connected with the blood-vessels. 



