AN INVITATION TO DINNER. 351 



The consideration, however, crops up before us, that if the fore- 

 going conclusions be correct, we should find our subject in the scales 

 to remain stationary so long as he performed no work at all. The 

 contention is a natural one ; but, unfortunately, it has no physio- 

 logical standing. There is no period of day or night during which 

 cessation .from work is possible to the body. If we suppose that the 

 Professor in the scales consented to trouble himself neither about to- 

 day nor concerning to-morrow, and to allow his muscles as well as 

 his cerebral organ to remain as thoroughly passive as might be, he 

 would still remind us of breakfast, lunch, and dinner; and, apart 

 from habit altogether, would feel perfectly ready and willing to join 

 us at table when the "joyful sound" of gong or bell reached his ears. 

 Nor would he be at any loss to reply to the obvious remark that, 

 as he had done no work, he could have no reasonable expectation of 

 participation in the delights of the table. He would require us to 

 note, firstly, that he had been working, even while resting ; secondly, 

 that this work was unavoidable ; and thirdly, that from its serious 

 nature it necessitated speedy repair. The Professor's heart for, 

 contrary to the opinion of the female portion of his acquaintance, 

 the eminent scientist possesses such an organ can be shown to per- 

 form in each twenty-four hours of his existence an amount of work 

 which can be legitimately termed of prodigious extent. Calculations 

 of very exact nature have been made regarding the work done by the 

 central organ of the circulation. The heart is a hollow muscle ; 

 hollow, to allow blood to pass through its chambers, and a muscle, 

 that it may contract to expel the blood forth into the vessels. The 

 heart's work is therefore as purely muscular work as is the lifting of 

 weights or the movements of walking. Now, the " unit of work," as 

 the basis of calculating the amount of labour expended in any given 

 action, is an expression which, plainly stated, may be taken to mean 

 that amount of energy (or " power of doing work ") required to raise 

 a unit of weight (i Ib.) through the unit of height (i foot). 



The heart is composed of four compartments or chambers. Two 

 are " auricles," which receive blood from body and lungs respectively, 

 and which propel the blood each into the larger chamber (or " ven- 

 tricle ") with which the auricle of each side is in free communication. 

 If the weight of the blood which is expelled by the sharp contraction 

 of each ventricle is multiplied by the height to which the blood rises 

 in a tube placed in communication with the outlet of the ventricle, 

 we obtain in the result the work done by each of these larger 

 chambers of the heart. It has been found that the height to which 

 the blood is sent in the tube is about nine feet. The weight 

 of the blood expelled at each contraction of the left ventricle of the 

 heart is about four ounces. The multiplication of these numbers, 

 therefore, gives us 2 \ foot-pounds that is, a force capable of raising 



