MUSCLES OF THE HIND LIMB !).-> 



in others. There is also occasionally (e.g. hornbills) an 

 additional attachment to the gastrocnemius. 



Ambiens. This muscle, as is well known, is not present 

 in all birds. Though the late Mr. GAREOD used it largely 

 in his scheme of classification, its mere presence or absence 

 is not an absolute guide to the systematic rank of the bird. 

 Broadly speaking, it is present in all the birds which 

 GAEEOD called homalogonatous, or normal-kneed, and 



gastr. 



Femur 



fi&ula. 



FIG. 52. LE<; MUSCLES OF Balearica (AFTER MITCHELL). THE 



AMBIEXS TEXDOX is CUT. 

 1, rtexor longus hallucis : 2-4, flexores perforati ; 2', ",' tk-xores perforati et perforantes. 



it is absent in all the birds which were termed by him 

 anomalogonatous, or abnormal-kneed. But there are excep- 

 tions, at any rate on one side. Thus while the muscle is 

 present in the storks generally it is absent from the nearly 

 related herons, and, indeed, is absent in three storks, Xenu- 

 rlnjnchus, Abdimia, and Dissura. When the muscle is 

 present it has as a rule the relations described above ; but 

 in a few birds it does not reach beyond the knee, thus 

 showing, perhaps, an incipient disappearance. The import- 



