KEPOET ON THE MARSUPIALIA. I •_'.". 



whilst five is the original number, there is a distinct tendency exhibited for the adductors 

 to disappear from the centre of the foot towards the margins, and this disappearance 

 takes place in a more marked degree in an outward direction towards the minimus than 

 in an inward direction towards the hallux. Thus the adductor hallucis and the adductor 

 minimi digiti are the most constant — the former or more internal of the two much more 

 so than the latter or more external. The adductor indicis and adductor annularis rank 

 next in point of constancy, but the adductor indicis, which is the more internal of the two, 

 is more frequently present than the adductor annularis. The central adductor, viz., the 

 adductor medii, was only found in three specimens. The sudden disappearance of this 

 adductor is probably due to the tendency which these muscles have to arrange them- 

 selves so as to act with reference to the middle toe. The exact ratio of constancy of the 

 different members of this group of intrinsic muscles can be seen by a reference to the table. 



Intermediate and dorsal layers. — At the end of Euge's paper upon the Deep Muscles 

 in the Sole of the Foot 1 there is the following statement : — " During the printing of this 

 work I notice that D. J. Cunningham divides the deep muscles of the mammalian 

 foot into three divisions — (a) plantar (adductores), (b) intermediate (fiexores breves), 

 (c) dorsal (abductores). I hold it incorrect to extend this subdivision to all mammals, espe- 

 cially since, even according to Cunningham, a fusion of layers b and c is very common." 



I fail to perceive wherein Dr. Ruge should consider this classification of the intrinsic 

 muscles " incorrect," seeing that throughout his two papers he indirectly admits it. Thus 

 he makes the great primary division into (1) contrahentes, and (2) interossei, and then he 

 divides the latter 1 into (a) a palmar, and (b) a dorsal series. Is this not a clear sub- 

 division into three layers, or in other words, a trilaminar arrangement ? The muscles 

 ;of the minimus and the muscles of the hallux he describes as 1 two separate groups. 

 AVhy he should consider the muscles of the marginal digits distinct from those of the 

 other toes I cannot understand. I have found no grounds upon which we can base a 

 difference, beyond the fact that from the more commanding position of these toes it fre- 

 cpiently happens (more especially in the case of the minimus) that their muscles have 

 undergone greater development, and it may be segmentation. 



Dr. Young of Manchester in answer to Euge's criticism remarks : — " It is difficult to 

 understand why the fusion of two previously existing layers, however common, should in 

 any way militate against the view that the separate condition was more typical than the 

 coalesced ; conversely, indeed, if the fact of their fusion be -in all cases established, it 

 , certainly seems to favour Dr. Cunningham's views of the type arrangement." I cannot 

 take advantage of this argument, forcible though it be, because I do not consider that we 



1 Loc. cit., p. 657. 



2 In his Memoir upon the development of the foot (loc. cit.) he says, " In the group of interossei pedis which at 

 present with general acceptance is divided into the four outer or dorsal, and the three plantar or inner, 1 include the 

 flexor hrevis minimi digiti, &c. &c." 



