AN INVITATION- TO DINNER. 349 



able repast. I may flatter myself that the "flesh-forming " and " heat- 

 producing " compounds, which physiology declares are necessary for 

 the support of my bodily belongings, will be represented to the full 

 in Smith's menu. The work of nutrition should be effected in the 

 most agreeable manner around Smith's hospitable board, where the 

 conversation of Caudal, for instance, may lend an additional and 

 mental zest to the physical delights implied in the repast proper. 

 But the physiologist steps in to inform me that even in the work of 

 food-taking there will be expended a very considerable degree of 

 energy. I shall be in the position of an engine which exhausts and 

 employs its steam, even in the act of laying in water and fuel for 

 future work. My digestion, I am informed a work that proceeds for 

 hours together will necessitate a large expenditure of nerve-force, and 

 of other forces as well. The act of converting food into a medium 

 (the blood) adapted to nourish every tissue, is thus in itself a piece of 

 tolerably hard work ; to say nothing of the labour performed by the 

 central engine of the circulation, the heart itself; or by the lungs and 

 chest in the act of breathing. Life would thus seem to be a kind 

 of process resembling that familiarly described as " burning the candle 

 at both ends." We " rob Peter to pay Paul," in our endeavour to 

 live wisely and well. One is reminded forcibly of that grim quota- 

 tion of Huxley from Balzac's " Peau de Chagrin," by the considera- 

 tion of the perpetual taking in and giving out which life seems to 

 involve. As the magic skin shrank with every wish of its possessor, 

 and ultimately vanished away together with the life it represented, so, 

 to quote Huxley, "all work implies waste, and the work of life 

 results, directly or indirectly, in the waste of protoplasm." And 

 again : " Physiology writes over the portals of life 



Debemur morti nos nostraque, 



with a profounder meaning than the Roman poet attached to the 

 melancholy line. Under whatever guise it takes refuge, whether 

 fungus or oak, worm or man, the living protoplasm not only ulti- 

 mately dies, and is resolved into its mineral and lifeless constituents, 

 but is always dying, and, strange as the paradox may sound, could 

 not live unless it died." 



One now begins to gain a glimpse of the fashion in which life 

 science answers the question, Why do we eat our dinner? When we 

 begin to conceive that the human body is, in one sense, a mere 

 machine, which performs elaborate and complex chemical and 

 physical work, and which, moreover, is always in action, more or less 

 completely, we are able to understand the basis on which physiology 

 rests its final reply concerning the philosophy involved in Smith's 

 invitation to dinner. But to render the position of the scientist still 

 more evident, we may inquire a little more exactly into some of the 



