REGARDED AS A MASS. 113 



ute : the stomach exercising its powerful chemistry : the 

 bowels silently propelling the changed aliment ; collecting 

 from it, as it proceeds, and transmitting to the blood an 

 incessant supply of prepared and assimilated nourishment ; 

 that blood pursuing its course; the liver, the kidneys, the 

 pancreas, the parotid, with many other known and dis- 

 tinguishable glands, drawing off from it, all the while, 

 their proper secretions. These several operations, togeth- 

 er with others more subtile but less capable of being inves- 

 tigated, are going on within us, at one and the same time. 

 Think of this ; and then observe how the body itself, the 

 case which holds this machinery, is rolled, and jolted, and 

 tossed about, the mechanism remaining unhurt, and with very 

 little molestation even of its nicest motions. Observe a rope 

 dancer, a tumbler, or a monkey ; the sudden inversions and 

 contortions which the internal parts sustain by the postures 

 into which their bodies are thrown ; or rather observe the 

 shocks, which these parts, even in ordinary subjects, some- 

 times receive from falls and bruises, or by abrupt jerks and 

 twists, without sensible, or with soon recovered damage. 

 Observe this, and then reflect how firmly every part must 

 be secured, how carefully surrounded, how well tied down 

 and packed together. 



This property of animal bodies has never, I think, been 

 considered under a distinct head, or so fully as it deserves. 

 I may be allowed, therefore, in order to verify my observa- 

 tion concerning it, to set forth a short anatomical detail, 

 though it oblige me to use more technical language, than I 

 should wish to introduce into a work of this kind. 



1. The heart (such care is taken of the centre of life) 

 is placed between two soft lobes of the lungs : is tied to the 

 mediastinum and to the pericardium, which pericardium is 

 not only itself an exceedingly strong mem.brane, but adheres 

 firmly to the duplicature of the mediastinum, and, by its 

 point, to the middle tendon of the diaphragm. The heart 

 is also sustaiiied in its place by the great blood-vessels which 

 issue from it.* 



2. The lungs are tied to the sternum by the mediasti- 

 num, before ; to the vertebrse by the pleura, behind. It 

 seems indeed to be the very use of the mediastinum (which 

 is a membrane that goes straight through the middle of the 

 thorax, from the breast to the back) to keep the contents 



* Keill's Anat. p. 107. ed. 3. 



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