THE FLUIDS OF THE BODY 49 



It suffices to say that lymph contains all the substances which 

 are present in the plasma of blood, but not necessarily in the 

 same total amount or in the same relative proportions. Speak- 

 ing generally, leucocytes are present in about the same numbers 

 as in blood 6,000 to 8,000 to the cubic centimetre ; but 

 leucocytes are everywhere present : in blood, in the lymph, 

 in lymph- vessels, in the tissue-spaces. As they are not 

 passively floating bodies like red blood- corpuscles, but active 

 migratory organisms, they tend to accumulate in one situation 

 and withdraw from another, in accordance with the opportuni- 

 ties which the different localities afford. They desert effused 

 lymph, blisters, ascitic fluid, and the like. They are not found 

 in the lymph in the pericardium. There are fewer in the 

 lymph coming from the intestines after a meal than in the same 

 lymph during the intervals between meals. Their departure 

 from effused lymph might easily be explained. It is not so 

 easy to account for their comparative absence from the lymph 

 in the lacteals when it is heavily charged with fat and other 

 products of digestion. Such leucocytes as are present at this 

 time are loaded with fat granules which they have stolen from 

 the chyle, as the lymph in the lacteals is usually termed. One 

 would need to be very intimate with a leucocyte before one 

 ventured to give reasons for all its movements. Lymph 

 contains the same proteid substances as blood, and in the same 

 relative proportions, but usually in smaller quantity. 



Incidental reference has been made to the great lymph-spaces 

 peritoneal, pleural, and pericardial. The brain and spinal 

 cord are separated from their outer membranes by a lymph- 

 space. There are also spaces within the brain the ventricles 

 and a central canal in the spinal cord. The aqueous and 

 vitreous humours of the eye are also lymph-spaces, although 

 the latter contains some remnants of tissue. The joint cavities 

 are lymph-spaces. So also are the bursse which surround 

 tendons or separate them from bones. It is not, however, 

 justifiable to include all these cavities in a single category, 

 either from the point of view of their purpose, their mode of 

 formation, or the nature of their contents. The peritoneal, 

 pleural, and pericardial spaces are parts of the great primitive 

 body-cavity, or coelom. The two first are potential rather than 

 actual. Normally they contain iust sufficient fluid to moisten 



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