146 ANATOMY FOR NURSES [Chap. IX 



spoken of as inflammatory exudate. Under these conditions a 

 death struggle between the leucocytes and bacteria takes place. 

 If the leucocytes are victorious, they not only kill the bacteria but 

 remove every vestige of the struggle, and find their way back to 

 the blood. If the bacteria are victorious, and suppuration ensues, 

 the leucocytes become pus corpuscles. Also, in the case of a 

 wound, the leucocytes, by virtue of their amoeboid movements, 

 escape from the blood-vessels, accumulate in the region of the 

 wound, and act as barriers against infection. 



Life cycle of the white corpuscles. — It is presumed that the 

 white corpuscles like all other cells have a definite term of existence. 

 We do not know the length of this term, or where they are de- 

 stroyed, except that large numbers are lost in the battle waged 

 against bacteria, others by hemorrhage, and others may be con- 

 verted into granulation tissue. These lost leucocytes are replaced 

 by new leucocytes which result from the division of former leuco- 

 cytes. This division usually takes place in the lymph nodes and 

 the spleen. 



Differences between white and red corpuscles. — 



(1) White blood-cells are larger than red corpuscles, but normally 

 are present in smaller numbers. 



(2) They have no pigment or haemoglobin, hence are colorless. 



(3) On account of the property of amoeboid movement their 

 shape varies. 



(4) They always have a nucleus, sometimes two or three nuclei. 



(5) There are five varieties that differ in microscopical structure 

 and possibly in function. 



(6) During circulation they keep close to and even seem to 

 adhere to the walls of the vessels, while the red corpuscles keep 

 in the middle of the stream. 



(7) By virtue of their amoeboid movement they escape through 

 the walls of the capillaries and are found in the tissue spaces. 

 They are also found in lymph, chyle, and pus. 



(8) The functions of the white blood-cells are quite different 

 from the red corpuscles. 



Blood-plates. — They are small, pale yellow, or colorless disks 

 of which little is known. They vary in size and shape, but are 

 always smaller than the red corpuscles. It is not decided whether 

 they are to be considered as independent cells or as fragments 



