THE BLOOD. 99 



protoplasm may grow up again and form a number of red corpuscles in a 

 similar way. 



(4.) From the tissue of the spleen. It is probable that red as well as 

 white corpuscles may be produced in the spleen. 



-(5.) From Microcytes. Hayem describes the small particles (micro- 

 cytes), previously mentioned as contained in the blood (p. 75), and which 

 he calls hsematoblasts, as the precursors of the red corpuscles. They ac- 

 quire color, and enlarge to the normal size of red corpuscles. 



Without doubt, the red corpuscles have, like all other parts of the 

 organism, a tolerably definite term of existence, and in a like manner die 

 and waste away when the portion of work allotted to them has been per- 

 formed. Neither the length of their life, however, nor the fashion of 

 their decay has been yet clearly made out. It is generally believed that 

 a certain number of the red corpuscles undergo disintegration in the 

 spleen; and indeed corpuscles in various degrees of degeneration have 

 been observed in this organ. 



Origin of the Colorless Corpuscles. The colorless corpuscles of 

 the blood are derived from the lymph corpuscles, being, indeed, indistin- 

 guishable from them; and these come chiefly from the lymphatic glands. 

 Their number is increased by division. 



Colorless corpuscles are also in all probability derived from the spleen 

 and thymus, and also from the germinating endothelium of serous mem- 

 branes, and from connective tissue. The corpuscles are carried into the 

 blood either with the lymph and chyle, or pass directly from the lymphatic 

 tissue in which they have been formed into the neighboring blood-vessels. 



USES OF THE BLOOD. 



1. To be a medium for the reception and storing of matter (ordinary 

 food, drink, and oxygen) from the outer world, and for its conveyance to 

 all parts of the body. 



2. To be a source whence the various tissues of the body may take the 

 materials necessary for their nutrition and maintenance; and whence 

 the secreting organs may take the constituents of their various secretions. 



3. To be a medium for the absorption of refuse matters from all the 

 tissues, and for their conveyance to those organs whose function it is to 

 separate them and cast them out of the body. 



4. To warm and moisten all parts of the body. 



USES OF THE VARIOUS CONSTITUENTS OF THE BLOOD. 



Albumen. Albumen, which exists in so large a proportion among the 

 . chief constituents of the blood, is without doubt mainly for the nourish- 

 ment of those textures which contain it or other compounds nearly allied 

 to it. 



