( 312 ) 



strated that such marks represent either absolute or relative eccentrical 

 areas. ConsequentJj I consider these marks to be eccentrical defect- 

 contrasts. The white marks in rabbits, to which attention has been 

 drawn by Winki.er, are of a very ditFerent nature, being expressions 

 of segmental variability ; in the series of equivalent segments, pro- 

 ducing pigment, one or two have lost this faculty ; thence results 

 the defect, corresponding in shape, distribution and extension with 

 the segmental analgetic areas. A further instance may be forwarded 

 by the so-called Lakenveld cows, whose white "cloth-covering" around 

 the trunk corresponds evidently with a series of pigment-less seg- 

 ments, which have become hereditary by artificial selection in breeding. 

 The above-mentioned white feet may be reckoned likewise to these 

 instances. In black dogs, horses or rabbits, white forefeet and a white 

 mark on the breast are frequently to be met with. E\'idently these 

 mean something more than a simple eccentrical defect. It cannot be 

 doubted that such cases represent phenomena of segmental omission. 



It is known by the experiments of Winkler ^) and myself that 

 the most eccentric skin-segments of the fore-feet (7^'' and ^^ cer\'ical 

 roots), consist only of the lateral portiojis of the dermatoma, the 

 dorsal parts having entirely vanished whilst the ventral parts are 

 lying exceedingly reduced at the ventral median line near the maiiubrium 

 sterni. Accordingly this relation corresponds perfectly with that of 

 the above described defect areas. For this reason I consider these 

 latter ones to be segmental defect contrasts ; they are the expression 

 of a segmental defect-varibility in the 7^^' and S^^ cervical segment. 

 Analogous cases are not rarely found. Frequently the white areas 

 are so extensive that eventually a defect of the 5*^ and 6'^' cervical 

 segment may be assumed besides that of the 7'^^ and S*^'^ . Analogous 

 relations exist in the posterior extremity, though we know less about 

 its segmental innervation. 



I cannot possibly in these pages enter into more minute details 

 concerning the question of the segmental distribution of the colour 

 marks in the skin. An extensive essay on this subject is shortly to 

 be published. The preceding explanations will however be of sufficient 

 aid to form a judgment concerning my fundamental views and to 

 understand the conclusions, stated in the following summary. Doubtless 

 these conclusions may have some importance for clinical work, 

 because they prove beyond any doubt the great significance of the 

 segmental innervation for the trophic condition of the skin, and add 



1) G. Winkler and G. van Rijnberk, Something concerning the growth of the 

 areas of the trunk-dermatoma on the caudal portion of the upper extremity. These 

 Proc. VI, p. 392. 



