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the preceding paragraph as they must obviously have an important 
bearing on the condition. 
In conclusion I would acknowledge my indebtedness to Professor 
Errıor Smitu for so kindly placing at my disposal the material for 
human dissection in the Anatomy Department at Manchester; to 
Messrs. JENNISON of Belle Vue for the apes on which I have worked 
and to Mr. Topp for kind and valuable assistance throughout the in- 
vestigation. 
Results. 
The consideration of the facts brought forward here, points to 
the following conclusions: 
(i) The extensor communis though inserted into the 2nd phalanx, 
is practically only an extensor of the 1st phalanx. 
(ii) Extension of the second phalanx is brought about by the palmar 
interossei aided by the dorsal interossei. 
(iii) Extension of the distal phalanx is brought about by the lum- 
bricals aided by the interossei (except the 1st and 2nd dorsal 
interossei). 
(iv) The extensores indieis and minimi digiti are two members of 
a series of four found in certain monkeys such as papio cyno- 
cephalus. 
(v) The lumbrical muscles were originally bicipital muscles, and this 
condition is generally retained in the case of the third member 
of the series. 
(vi) The insertion of the corresponding muscles in the foot is similar 
to that in the hand, but simpler owing to the reduced complexity 
of movement of the toes. 
It is convenient here to enumerate the actions of the several 
muscles which have been discussed in the present communication. 
Extensor Communis—Extends the 1st phalanx of each finger. 
Extensor Indicis—Extends all phalanges of the index. 
Extensor Minimi Digiti— Extends all phalanges of the little finger. 
Lumbricals—Extend distal phalanges. 
Palmar Interossei—Flex 1st, and extend remaining phalanges. 
Adductors. 
Dorsal Interossei—Flex 1st, and extend other phalanges. Abductors. 
