THE INTEGUMENT AND THE EXOSKELETON 103 



always so arranged that the hairs converge at two opposite 

 corners and diverge at the other two. A feathering is a spe- 

 cial form of area, usually more extensive than the two last, 

 occurring only in association with a vortex, of which it forms 

 a continuation in one direction. It is in the form of a long 

 and narrow ellipse, and the hair currents run along a central 

 axis and diverge to the margin. 



All of the above forms may be readily seen upon our do- 

 mestic animals, and are often well marked in man, especially 

 in individuals whose skin is covered with very short appressed 

 hairs. An especially good object is the broad, square chest 

 of the bull-dog, on which are usually three vortices and three 

 rhomboids ; a vortex above and a rhomboid below in the me- 

 dian line, a lateral rhomboid on each side of the vortex, and 

 a lateral vortex on each side of the rhomboid. Aside from 

 these there occurs a vortex on each elbow, usually one on each 

 side of the neck, and upon the hinder parts a pair of especially 

 conspicuous vortices, above which, at the base of the tail, 

 are two rhomboids. Individual variation may show depar- 

 tures from this description. 



In Man the various features are present and often well 

 marked, but as they require for their expression a certain 

 grade of pilosity, they are usually overlooked. Here, also, 

 as in other animals, there is considerable individual variation, 

 and a feature marked on one person may be absent on another ; 

 the two sides, also, are not necessarily symmetrical. The 

 most conspicuous vortex is the one at the crown of the head, 

 easily observed in boys with short hair. This may be either 

 clockwise or contra-clockwise, and seems to follow no rule 

 in this respect. Other vortices occur above the angle of the 

 jaw and in front of the axilla. Rhomboids occur along 

 the mid-ventral line; one of them is situated at the angle 

 between the throat and the chin, immediately above the thy- 

 reoid protuberance, a second at the anterior end of the sternum, 

 and a third on the abdomen, midway between the umbilicus 

 and the pubic eminence. A rhomboid is found constantly upon 

 the lower part of the ulna, a little above the wrist. 



