CHAPTER V. 



BLOOD AND LYMPH. 

 BLOOD. 



ALTPIOUGH strikingly different in physical char- 

 acter from most animal tissues, we must yet regard 

 blood and lymph as true tissues tissues with a fluid 

 intercellular substance. Let us first consider the 

 blood. 



In normal human blood we find suspended in a 

 colorless fluid, the plasma, three distinct kinds of 

 formed elements: I. Colorless blood-cells ; 2. r ed blood- 

 cells ; 3. blood placques. 



i. Colorless or White Blood-cells or Leucocytes. 

 These are small, usually spheroidal nucleated cells, 

 without a membrane, the cell-body being finely, or 

 sometimes coarsely, granular. The nuclei, of which 

 there may be one or more, are not usually visible in 

 the living cells on account of the granular character 

 of the body which conceals them, and are of vary- 

 ing form, sometimes spheroidal or dumb-bell- 

 shaped, sometimes having the form of a bent or 

 twisted cylinder, and again entirely irregular. 



These cells possess the power, under favorable 

 conditions, of spontaneous movement. They change 



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