CHAP. IV] THE GENERAL ANATOMY OF THE LEMUROIDEA 71 



eminences, which seem in their origin to have developed rather in 

 relation to the rapid movements of a quadrupedal animal 1 . 



The papillary ridges in the Lemurs are said by Schlaginhaufen 

 to arise through the coalescence of minute eminences at one period 

 isolated from each other. Indeed a survey of the lemurine " planta" 

 will suggest (Fig. 39) such an origin at once. But the " islands " 

 thus described have a further definite character, since they them- 

 selves are marked by the orifices of several ducts (of sweat-glands) 

 arranged more or less regularly in a circle. This feature, together 

 with others of an histological nature, justifies their distinction as 

 " insulae lenticulai'es " from another variety in which but one 

 orifice and duct are present. The latter are called " insulae 

 primariae " (Schlaginhaufen). It is noteworthy that the papillary 

 ridges of the Lemurs are derived from such lenticular islands, 

 whereas in the closely-allied Lorisinae (the so-called Slow-Lemurs) 

 and in Man himself, the corresponding role is played by insulae 

 primariae. The papillary ridges thus constituted traverse the 

 several pads and also the larger nodules of the lemurine palm and 

 sole. There they give rise to certain patterns (figurae tactiles) 

 (Figs. 38 and 39), which may now be described briefly. 



On the vola (palm), the ridges tend to the production of the 

 appearances of concentric circles or inosculating loops. These 

 are arranged on the proximal and interdigital pads, and in the 

 centre of the vola the lines tend to run transversely across the long 

 axis of the hand. The finger tips or apical pads are marked by loops 

 (sinus primarii) which are widely open (long lineae communicantes). 

 They enclose many longitudinal ridges (fasciculi centrales) and are 

 found on the digital apex and even on the dorsal aspect as far as 

 the edge of the nail. 



The skin over the phalanges is nodulated and irregular. A 

 few paired nodules bearing papillary ridges are seen here on each 

 finger save the second. The ridges converge distally to the axial 

 line of the digit. 



On the planta (sole of the foot) the papillary ridges on the 



1 This view, viz. that the prime value of papillary ridges resides in their em- 

 ployment as sense-organs of touch, does not necessarily exclude the more mechanical 

 influence they may possess, in rendering foot-hold or hand-hold more firm and less 

 likely to slip. 



