MINUTE ANATOMY OF PAPILLARY RIDGES 81 



Case 2.— Right and left foot of the same subject examined. The right 

 shows more imbrication on the plantar surface and less on the digits. The 

 left shows little or no imbrication on the plantar surface, and more on the 

 digits. 



Case 3. — Right and left hand of the same subject examined. Both 

 show almost exactly the same amount of distal imbrication on the digits 

 and one shows a small area of proximal imbrication. Palmar surface of 

 one shows one more small eminence at the base of a digit, with distal 

 imbrication, than the other. 



Among the various specimens examined microscopically 

 the hand of one working man and the foot of another, in which 

 the epidermis was much thickened by mechanical pressure, 

 showed no imbrication of the ridges among upwards of fifty 

 sections taken from these two subjects. Such a result as this, 

 naturally suggests that the phenomenon in question is one which 

 may have some explanation in the dehcacy or otherwise of 

 the uses to which the hand and foot are apphed in different 

 classes and individuals. The examination of the matter is a 

 slow and rather laborious one and if pursued so as to estabhsh 

 any generaUsation would require much application of time and 

 trouble. 



The meaning of this variable imbrication of papillary ridges, 

 will be considered in the physiological part of this work, and it 

 is here only necessary to point out certain of the most notable 

 sections from the skin of the mammalian hand and foot, in 

 which the phenomenon in question is found. 



Great Ant-eater. — The earliest mammal in which I have been 

 able to find imbrication of the palmar or plantar skin is an 

 Edentate, the Great Ant-eater ; and two illustrations of this 

 are seen in Figs. 76, 77. There are no papillary ridges here, 

 but the hard palmar and plantar epidermis is covered with 

 flat scales which show a distal imbrication and it will be 

 observed also, that the papillae of the corium preserve a corre- 

 sponding slant. 



Rodents. — Among Rodents, many forms show well-marked 

 transverse ridges on the digits with a distal imbrication, as in 

 Microtus, Mus fnusculus, Mus decumanus ; but these again are 

 not true papillary ridges. 



