ABSORPTION. 295 



is deficient, plethora is the result. In the later periods of 

 life it is more active than nutrition, and the body dwindles 

 in size ; in youth the reverse is the case. 



12. Foreign bodies, introduced into the substance of or- 

 gans, are also absorbed. Wens and tumours of considera- 

 ble size, often disappear from the same cause. Instances 

 are known where the absorbent vessels have set to work and 

 removed the whole bone of a limb ; and but lately a case 

 occurred in Boston, in which every particle of bone in the 

 arm was thus taken up and carried away, after a fracture 

 had occurred. How admirable is that arrangement by 

 which the vessels of absorption and secretion so act as to 

 balance each other ; and how soon would a loss of this 

 balance produce derangement, disease, and even death. 



13. Another form of absorption is called respiratory, 

 which we have already considered under the subject of res- 

 piration. We understand by itmerely the introduction of 

 oxygen into the blood, through the pulmonary cells) Sub- 

 stances, however, in a state of vapour, or fine dust, are also 

 readily imbibed when drawn into the lungs ; such as metal- 

 lic vapours, oderiferous particles, marsh and other effluvia. 

 It is in this way, probably, that contagious diseases are 

 caught. 



14. It is by means of what physiologists call recrementi- 

 tidl absorption, hat fluids are removed from the system 

 which are secreted upon surfaces that have no external out- 

 let as in the cavity of the chest, abdomen, brain, &c. 

 These fluids are various : such as the serous fluids ; the sy- 

 novia of the joints ; the fat ; the marrow, and the humours 

 of the eye. It is this which prevents dropsies in these vari- 

 ous cavities ; and also removes them when already existing. 

 This form of absorption is also proved by the fact, that fo- 

 reign substances, placed in contact with these surfaces, in a 

 short time disappear. 



15. Another variety of absorption has been called 

 menttiicd ; as{it relates to the fluids which have been excrel 



