HANDBOOK OF PHYSIOLOGY. 



Colorless corpuscles are also in all probability derived from the spieen 

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



Fio. 85. Further development of blood-corpuscles in connective-tissue cells and transformation 

 of the latter into capillary blood-vessels, a, an elongated cell with a cavity in the protoplasm oc- 

 cupied by fluid and by blood -corpuscles which are still globular; 6, a hollow cell, the nucleus of 

 which has multiplied. The new nuclei are arranged around the wall of the cavity, the corpuscles 

 in which have now become discoid; c, shows the mode of union of a " hsemapoietic " cell, which in 

 this instance contains only one corpuscle, with the prolongation (bt) of a previously existing vessel; 

 a and c, from the new-born rat; 6, from the foatal sheep. (E. A. Schafer.) 



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

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



FIG. 86. Colored nucleated corpuscles, from the red marrow of the guinea-pig. (E. A. Schafer.) 



phatic tissue in which they have been formed into the neighboring 

 blood-vessels. 



1. Uses of the Blood. 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. 



