THE LYMPH AND LYMPHATIC SYSTEM 335 



bringing back to the heart the liquid exudation which 

 escapes into the tissues from the finest blood-vessels 

 (Fig. 43). 



Whilst we distinguish in an animal body various 

 " tissues " which have special properties and activities, 

 and can be dissected out and delimited — as we could 

 dissect and distinguish the " tissues " (flannel, silk, 

 leather, whalebone, wadding, gold-thread, etc.) making 

 up an elaborate padded, stiffened brocaded, lined, and 

 decorated costume — we find that, unlike what is usual in 

 a man-made costume, all the parts of an animal body 

 (viscera, and their lobes and sub-divisions, the blood- 

 vessels, nerves, muscles, bones, etc.), are covered and 

 separated from one another, and, at the same time, held 

 together by a ubiquitous soft, spongy tissue, consisting 

 of delicate threads and bands, enclosing spaces — some 

 excessively minute and narrow, others larger— in which 

 is a liquid. This is the great packing tissue of the 

 body, and is called "the connective tissue." Its threads 

 and bands have delicate, usually flat nucleated corpuscles 

 (so-called " cells ") of transparent protoplasm resting 

 upon them and bathed by the liquid in the fine spaces. 

 The threads and bands are, indeed, the product of the 

 protoplasmic cells, built or " spun " by them, laid down 

 by them as a snail leaves a slimy smear behind it as 

 it crawls. It is not difficult to cut out transparent 

 pieces of this " connective tissue " from a recently killed 

 animal and to examine it with a very high power of 

 the microscope. You may then see the living proto- 

 plasmic corpuscles slowly "streaming" and changing 

 shape, and sometimes dividing (one into two) so as to 

 form new corpuscles. 



I made my first acquaintance with them when I was 



