DICHOTOMY. 129 



represented in fig. 73, a third hind limb projecting 

 posteriorly between the normal legs. On dissection it 

 was found attached by muscle and tendon to the 

 symphysis pubis : it presented the usual segments of 

 femur, crus, and pes, and was furnished with two 

 well - formed digits and the rudiment of a third. 

 During life it was found that when the skin of the 

 limb was stimulated the frog would jump quickly 

 away ; sometimes oft-repeated stimulation would call 

 forth a muscular contraction 

 in the limb. Occasionally 

 movements were observed 

 in the abnormal limb when 

 the frog was left entirely to 

 itself. 



It has already been men- 

 tioned that in parasitic 

 foetuses, even when the 

 limbs are well-formed, the 

 autosite has rarely the power 



- , . FIG. 73. A Frog (Rana palustris), 



Of Spontaneously moving with % U p er numerary hind limb, 

 the limbs belonging to the (After Tuckerman). 



parasite, and this is the rule in supernumerary limbs, so 

 that the spontaneous movement in the leg of Tucker- 

 man's frog is interesting. The drake (fig. 74) pos- 

 sessed the power of moving the abnormal limbs, and 

 similar specimens have come under my notice in hens. 

 Such power is, however, exceptional. 



Supernumerary pelvic limbs similar to those of 

 frogs and toads, sheep and birds, occur in the human 

 subject ; several of the individuals thus affected have 



10 



