MISCELLANEOUS NOTES. 347 



mechanism the equilibrium would be unstable. The tail produces this 

 accommodation for by hanging vertically down behind, it gives to the hind 

 body that additional weight sufficient to counteract the excess in the fore 

 body. Were the tail curled forward over the back, as occurs when the 

 animal is resting on a broad and firm surface, then a still additional weight 

 would be thrown to the front and the balance would be disturbed and at 

 the same time the elevation of the tail would raise the centre of gravity of 

 the animal, and this would still further tend to increase its instability. The 

 tail, therefore, in this position, maintains the bodily balance and does so m 

 two ways ; by the addition of weight to the posterior part of the body and 

 by lowering the centre of gravity of the animal, both of which tend to the 

 production of a greater stability. It is interesting to place a captured 

 squirrel of this species on a smooth cylindrical metal bar into which its 

 claws cannot penetrate or can scarce obtain a foothold and to observe the 

 beautiful equilibrium of the body and the great part played in its main- 

 tenance by the downward prolongation of the bushy tail. It can be 

 immediately recognised that the position of the tail is not due to the sole 

 effect of gravity forcing it to hang downwards, but that it is fixed there by 

 a definite voluntary muscular action and the distinct resistance offered by 

 the animal towards any artificial attempt to raise the tail from its normal 

 position cannot be mistaken. 



But the function of this organ as an agent for the preservation of the 

 hodily equilibrium deserves a little further consideration. Should the 

 animal, when seated on a thin b tan ch, stretch forward its head and fore 

 body to an unusual degree, then the tail is immediately elevated, the hind 

 arm of the lever is consequently lengthened and the general equilibrium 

 directly restored. Should, on the other hand, the reverse movement occur 

 and the hind quarters of the animal extend abnormally backwards and tend 

 to overbalance the anterior portion of the body, then the tail is immediately 

 swept forwards beneath the branch and thus succeeds in recovering the 

 halance. In this latter case, it might have at first been considered that the 

 very characteristic movement of the tail over the back would be equally 

 efficacious in producing this result, but a movement's reflection will show 

 that such a movement would primarily be associated with an elevation 

 and backward prolongation of the tail which would tend to further in- 

 crease the bodily instability, and it wovild later, when the tail bacame 

 curled over the back, bring about an elevation of the centre of gravity 

 which would add still more to this undesirable result. A lateral inclination 

 of the body to the right is counteracted by a gentle movement of the tail to 

 the left and the converse is likewise true. The whole length of the organ 

 IS under a continuous voluntary muscular control, every tendency to over- 

 balance in one direction is met with a counterbalance of the tail in the 

 opposite direction and a uniform equilibrium, beautiful in its physical 

 simplicity, yet marvellous in its nervous and muscular complexity, is thus 

 attained. It is instructive to observe a squirrel of this species leaping and 

 clambering from branch to branch and to endeavour to follow the motion 

 of the long tail as it sways backwards and forwards, to the right and to 

 the left, and to recognise that its slightest movement is directed towards 

 some object, is to attain some end. On occasions the animal may reach 

 a still more difficult position, where its every effort and all its powers of 

 balance must be forced into action in order to retain the bodily eqinlibrium, 

 and then, as it staggers on its insecure support, the tail is thrown into a 

 series of rapid and complicated movements which perplex the mind in the 

 endeavour to follow them. But by no means so easily as by a simple 

 experiment can this balancing function of the tail be immediately demon- 

 strated. If in a captured animal the tip of the tail be fastened to the 



