184 SPECIAL PHYSIOLOGY. 



followed by the submergence of those parts. The smallest exertion 

 of the feet in a treading motion, suffices, however, even under these 

 circumstances, to keep the face above the surface; and, if aided by 

 the hands, this is still more easily accomplished. The buoyancy of 

 the body is however so slight, in other words, its specific gravity is so 

 little lighter than that of water, that, to maintain the face above the 

 surface, every other part must be submerged; for if, whilst thus sup- 

 ported, one arm be extended out of the water, the head immediately 

 sinks in a corresponding degree. 



In the act of swimming, the body lies, with the abdomen downwards, 

 in, but near the surface of, the water, and not quite horizontally, the 

 head being inclined somewhat upwards, and thrown back, so as to sink 

 as much of the hinder part of the cranium as possible, and to throw 

 the face alone, with the breathing apertures, the nostrils and mouth, 

 upwards and forwards out of the water. A progressive motion is then 

 accomplished, by placing the hands together in front of the sternum, 

 darting them forwards in the middle line, and then sweeping them 

 outwards, with the fingers in contact, and the palms everted and 

 turned slightly downwards, through a part of a circle, and lastly, 

 bringing them quickly inwards to the front of the sternum again. In 

 the meantime, whilst the arms are being extended forwards, the legs 

 are drawn under the body, close together, with the feet extended, and 

 then, are thrust powerfully backwards and outwards, with the feet flat, 

 at the same moment that the arms describe the part of a circle back- 

 wards. The combined propulsive action of the anterior and posterior 

 limbs, moves the body forwards, and slightly elevates the head at each 

 stroke; at this moment, inspiration and expiration should be accom- 

 plished. Swimming may also be performed on the back, with all four 

 limbs, or on the side, using only one arm, but both hinder limbs. 

 These modes of swimming are less rapid, but quieter, easier, and less 

 exhaustive, than the ordinary mode on the face. The rate of motion 

 of a swift swimmer is surprising, especially when it is considered that 

 the rounded form of the human body is not well adapted for cleaving 

 the water. 



Locomotion of Animals in Fluids. 



In swimming, land quadrupeds generally have this advantage over man, 

 that, owing to the length of their neck, they can more easily maintain the 

 orifices of the respiratory passages above the water. They also swim by an 

 action of all four limbs, precisely similar to that which they habitually employ 

 in locomotion on land, so that no training, as it were, is necessary for them 

 in the art of swimming, but they swim quite naturally on first entering the 

 water ; whereas in man, the movements performed in that act, are so special 

 and so different from the ordinary movements of locomotion, that he requires 

 instruction and practice to accomplish them successfully ; hence a land quad- 

 ruped, when thrown for the first time into water, swims with tolerable ease 

 and certainty ; whereas a human being, if. uninstructed, even if he succeeds 

 in floating, cannot accomplish any definite progressive motion through that 

 fluid. 



Certain quadrupeds fitted for an amphibious mode of existence, such as the 

 otter, beaver, seal, and water-rat, have their limbs specially adapted for that 

 purpose. In the two last-named animals, the feet are small, and the toes 

 partially webbed ; in the otter, the toes are distinctly webbed ; in the seal, the 



