132 



PRINCIPLES OF ANIMAL BIOLOGY 



or more to flow from the leg to the vein in the shoulder, a.s compared 

 with less than a minute for the blood to make a complete circuit from 

 heart to heart. 



Interrupting the lymph vessels are numerous enlargements made of 

 connective tissue, called lymph nodes, which filter out or otherwise remove 



the solid particles in the lymph. In these nodes 

 one of the kinds of white blood cells (Fig. lOOC) 

 is created. In the nodes any bacteria which 

 escape destruction by white corpuscles at the 

 seat of infection are apt to be destroyed, and 

 nodes are often swollen during an infection. 



Connected with the lymph vessels is a set of 

 tul:)es Avhich originate in the walls of the small 

 intestine. These are the lacteals (Fig. 990, 

 which are part of the lymphatic system. They 

 extend into the minute fingerlike projections 

 (the villi, Fig. 91) in the walls of the intestine 

 and are especially useful in absorbing digested 

 fats. These lacteals collect into larger vessels 

 and finally merge with the lymph vessels of the lower part of the body, 

 at a point shortly below the lowest rib. Their contents are thus 

 disgorged into the left one of the veins which receive lymph. 



Fig. 106. — Lymph cap- 

 illary, diagram of short 

 segment above, photo- 

 graph of single valve be- 

 low. {Photograph by cour- 

 tesy of General Biological 

 Supply House.) 



References 



Carlson, A. J., and V. Johnson. The Machinery of the Body. University of 



Chicago Press. (Chaps. III-V.) 

 Mitchell, P. H. General Physiology. 3d Ed. McGraw-Hill Book Company, Inc. 



(Chap. XIX, chemistry of blood and lymph; Chap. XX, the circulation.) 

 Rogers, C. G. Textbook of Comparative Physiology. 2d Ed. McGraw-Hill 



Book Company, Inc. (Deals largely with invertebrate animals: Chaps. X and 



XI, the blood; Chap. XII, coagulation; Chap. XIII, circulation; Chap. XIV, 



heart action.) 



