Jantaky 1, 1001.] 



KNOWLEDGE 



they are so arranged as to bo parallel to the axis of the 

 object grasped. As rcgai'ds this fuuctiou of the papil- 

 lary ridges. Dr. Hepburn observes that although they 

 are conipai^atively low, " yet they must cause a certain 

 amount of friction, and thereby prevent slipping, while 

 the naturally moist and clammy condition of tlic palm 

 and sole of monkeys must be of material assistance to 

 the firmness of the grasp. A man instinctively moistens 

 the palms of his hands when he wishes to make his 

 gi-asp more scciu-e ; and the grasping power of monkeys 

 must be considerably increased by the application of 

 numerous jiapillary ridges which are capable of intimate 

 adaptation to the surface of the object grasped." 



In a later passage the same observer adds tliat, apai't 

 from the hook-like manner in which the orang-utan 

 and the American spider-monkeys employ their hands 

 in trapeze-like movements, there can be no doubt that 

 the palms are capable of a considerable amount of 

 lateral folding, as is proved bj- the creases to which 

 allusion has been already made. And it appears pro- 

 bable that the papillary i-idges ai'o designed to afford 

 increased firmness of grasp when the palms are thus 

 folded. Consequently, simple transverse ridges on the 

 palms, except in the second joints of the fingers, are 

 conspicuous by their absence ; and we find instead the 

 complicated patterns on the eminences already described. 



A somewhat different type of arrangement obtains 

 in the hand of the South American spidci'-monkeys, 

 in which the thumb is wanting. In this group it will 

 be noticed (Fig. 4) that although whorl-liko patterns 



Fio. 4.— Kiglit Palmiir Impri'ssion of a 

 Spider Monkey (Alelea nlerj. 



z.Tt> observable in the interdigital eminences, yet they 

 are much smaller and less distinct than in ordinary 

 monkeys; the same being the case with the ulnar 

 eminence. The radial pattern, at the inner side of the 



thumb is, however, practically wanting, owing doubtless 

 to the absence of that digit. It will further be noticed 

 from an examination of the figure tliat elsewhere on 

 the palm, not even excepting the fingers, the general 

 arrangement of the ridges is longitudinal. Since the 

 hands of the spider-monkeys are, as already mentioned, 

 largely used in a hook-like ni;uiner during the arboreal 

 evolutions of those active creatures, it would seem at 

 first sight that the arrangement of the ridges precisely 

 controverts what has been said above as to their being 

 pai'allcl with the long axis of the object grasped. But 

 the palms of even these monkeys, as is indicated by the 

 numerous creases, are evidently much folded laterally; 

 and it must also be borne in mind that an equally 

 important function of the hand is the plucking and 

 holding of spherical or sub-spherical fruits. And for 

 such a combination of functions the mode of arrange- 

 ment of the ridges is doubtless the one that is most 

 suitable. If the ridges were transverse the fruit would 

 very probably have a tendency to slip out of the hand 

 on one side of the other; but this is clearly prevented 

 by the longitudinal arrangement. 



The above ai'e the chief modifications displayed by 

 the palm-prints of monkeys ; and it may bo added that 

 a very similar general plan of ai'rangement of the 

 papillary ridges and grooves obtains on the sole of the 

 foot of these animaJs, subject, however, to such modifi- 

 cation as is necessary for the different function of the 

 foot as compared with the hand. But in some at least 

 of their allies, the lemuroids, as represented by the true 

 Icnjurs of Madagascar, the galagos and pottos of Africa, 

 and the lorises and tarsier of A.sia, a very curious dc- 

 pai'turc from this arrangement obtains. In regard to 

 the true lemurs it is generally stated that on the outside 

 of the palm of the hand and under the base of the 

 fingers are situated fleshy pads, giving them greater 

 grasping power. This, however, is scarcely an adequate 

 statement of the true state of the case. Fig. 5 shows 





'h 



Fio. 



— Riglit Palm-print ol' Keil-fronted 

 Lemur (Lemur rvjifruns.) 



the palm-impression of the icd-f rented lemur-, a well- 

 known Malagasy species. In this it will be seen that 

 the balls of the digits are expanded into largo convex 

 circvdar pads upon which are a number of papillary 

 ridges; but instead of these ridges covering the whole 

 surface of the pads, they are interrupted by an irregular 

 nei>work of relatively large canals, producing the white 

 lines in the impression. On the palm of the hand are 

 seen the three interdigital eminences of the monkey's 

 hand, together with a large radial and a somewhat 



