122 PHYSIOLOGY OF ORGANIC: LIFE. 



of moving itself; following, without resisting, 

 the impulse it receives from the vessels in which 

 it is contained. It has the capacity of being 

 changed by the power of the part in. which it is 

 deposited ; yielding without resisting, as the 

 softened and adapted wax to the force of the 

 impression engraven on a seal. It bears the 

 same relation to the secretory organs, as air 

 does to the organs of sound ; if the air expired 

 from the kings, inherently possessed any parti- 

 cular sound, that particular sound would con- 

 stantly manifest itself; but air being destitute 

 of all sound, retains the capacity alone of being 

 expanded and compressed ; it thereby becomes 

 fitted to be acted upon by the organs of speech, 

 and through their power it is modulated and 

 harmonised, arid language ultimately produced. 

 It is with a view of preserving this aptitude 

 in the blood of animals, and of preventing the 

 sensible qualities which the coarser parts con- 

 tain, from being employed; or exerting any in- 

 fluence upon the organs ; that we behold the 

 design and end for the exhalent termination of 

 arteries in capillary tubes ; by means of which 

 a mechanical cause exists to prevent a mechani- 

 cal and deleterious effect. If it were not for this 

 mode of construction ; if the terminated diame- 

 ter of the exhalent arteries w^ere large instead of 

 small, not only the more tenuous, but the more 

 globular parts of the blood w r ould be permitted 



