322 A Manual of Veterinary Physiology. 



through a great distance, or through a certain distance with 

 great precision, rather than moving heavy weights through 

 a short distance (Foster). In connection with this we may 

 say that the weight of the fore-leg, cut off at the elbow, of 

 a cavalry horse was found to be 17 lbs. 8 oz. : cut off at 

 the knee, through the upper row of bones, it was found to 

 weigh 7 lbs. 10 oz. : one fore-foot with corona weighed 

 2 lbs. 3 oz., and the hind-leg, cut off' at the hock-joint, 

 weighed 10 lbs. 9 oz. 



It is very necessary to be clear on this question of levers, 

 and not to adopt too rigid a mechanical view of them. The 

 point of importance to which I would draw attention is, 

 that what will form a lever of one order in a certain posi- 

 tion of limb, forms a lever of another order in a new 

 position. We have given examples of this in the triceps 

 extensor brachii acting in the one instance as a lever of the 

 first order, and then as one of the second. The nature of 

 the lever depends upon the position of the body, so that 

 Colin proposes the term ' alternative lever.' He also speaks 

 of a ' composite lever,' where the power in the same position 

 of limb acts in two distinct ways, and he gives as an 

 example the flexor metacarpi externus acting as a lever of 

 the first order above the knee through its insertion into 

 the trapezium, and as a third order of lever below the knee 

 through its insertion into the external metacarpal bone. 



The same care must be taken also in viewing muscles 

 simply as extensors or flexors. Stillman points this out 

 very clearly, and lays stress on the fact that some muscles 

 may act as flexors and extensors at the same time, and he 

 very rightly impresses the importance of taking into con- 

 sideration in animal locomotion some other action of 

 muscles than that of flexion, extension, adduction, and ab- 

 duction, viz., the function. of propelling, which he believes to 

 represent 85 per cent, of the work of the horse's muscles. 



It, is most important, however, to remember thai pro- 

 pelling is not a power apart from flexion and extension, but 

 the result of them. 



The difference existing between the articulation of the 



