,li8 THE DISEASES AND DISOEDEHS OF THE OX. 



organ. The anthropoid apes, moreover, have the tail only 

 poorly developed. Again, the shape of the rudimentary tail 

 changes as prone animals become erect, in such a manner that 

 it serves in some degree to support the pelvic structures. 



In the hind limbs of quadrupeds the circulation of the blood 

 is feebler than in the fore limbs. Possibly the erect posture 

 in man may still further impede the circulation of blood in 

 the lower limbs. Hence, we may explain the frequency with 

 which gouty deposition in man generally first occurs where the 

 circulation is most sluggish. 



Furthermore the erect posture affords a freer play to the 

 movements of the fore extremities. The late Dr. Kolleston used 

 to teach that this additional freedom had removed the necessity 

 for the continuance of the development of the panniculus 

 carnosus, which muscle is useful in ridding the skin of some 

 parasites, also in certain defensive and offensive operations, as 

 for instance in the erection of the spines of the Diodon, the 

 scales of serpents, and of the Manis, the quills of the porcupine, 

 and the bristles of the hedgehog. Human beings, however, in 

 virtue of their erect posture, possess so much more freedom of 

 movement of the fore extremities than have prone animals, that 

 this muscle has atrophied in them as a result of falling out of use. 

 The fact that man has remnants of this muscle in the platysma 

 myoides and, according to Henle, in several muscles of the head, 

 is to be considered in relation with the fact that hairs still flourish 

 on the head, the face, and upper part of the neck. Birds, how- 

 ever, are erect, and yet some have a remarkably well developed 

 panniculus carnosus. An albatross was found by Dr. D. Astley 

 Gresswell to have large tendons inserted into its feathers and 

 into its skin. It is, however, very clear that in birds the fore 

 limbs are specialised for flight ; their freedom of movement in 

 other directions being consequently correspondingly curtailed. 



Man is right-handed, as indeed also are quadrupeds, though 

 to a far less extent. In human beings, the fore limbs, being 

 much freer than in animals, have acquired far greater inde- 

 pendence of action. The fact that the right limbs have taken 

 on the more complex tasks is attributed to the left side of the 

 brain receiving a more direct supply of blood, and this view is 

 strengthened by noting the frequency with which embolism 

 occurs on the left side of the brain, as compared with its less 



