416 THE EXTERIOR OF THE HORSE. 



Conditions of the Economical Production of Work. — 

 Let us attempt now to determine what must be exacted from the 

 motor, in 'order that he may produce, in the best conditions, the 

 greatest amount of work with the least possible fatigue. In other 

 words, let us see under what circumstances the work will be the least 

 onerous for the animal, and therefore the most economical. 



Professor Baron ' has well explained this important question. In 

 his opinion resistance to fatigue is more or less a, function of the fol- 

 lowing conditions : 



a. A powerful faculty of dynamic accumulation of the nervo-muscular 

 system, — blood. 



b. Innate or acquired ability of the muscular fibre to make use at 

 once of the nervous or plastic elements (excitable, firm, dense muscles ; 

 rapid reflex action). 



c. A good construction of the members and beautiful propositions 

 (perfection of the mechanism rendering it fit to act with force, ease, 

 precision). 



d. Innate or acquired ability of the organism to rid itself quickly 

 and thoroughly of the waste materials through its emunctories (spacious, 

 active lungs ; surface of the body relatively extensive). 



e. Facility of the locomotory apparatus to execute easily certain 

 movements (training of the horse ; economy of force and time for the 

 execution of a determined work). 



/. The quality of the food and that of the tissues, both of tvhich tend 

 to lessen the formation of the waste matters or permit the organism to rid 

 itself of them at shorter intervals (substantial food of little bulk ; a 

 good assimilation). 



The horse which will answer best to all these conditions will also 

 be able to perform the greatest work and resist for the longest time 

 the fatigue which results from it. 



Endurance in Different Kinds of Animal Motors. — Does 

 endurance ofler the same interest in horses of force as in those of 

 speed ? Incontestably it does not, and it is not difficult to understand 

 this. In animals which are utilized only as force factors the muscular 

 contractions are slow, inextensive, not frequent, and of an intensity 

 rarely excessive. Their work increasing in proportion to the weight to 

 be dis})laced, their speed is always very ordinary. Consequently, their 

 expenditure is never very great in ordinary circumstances. When it 

 becomes so, — for example, when they have to ascend an acclivity or 



' R. Baron, loc. cit., p. 756. 



