145 
Nachdruck verboten. 
The Action of the Extensor, Lumbrical, and Interosseous Museles 
in the Hand and Foot. 
By Ricaarp Wiırran, 
Prosector in the Anatomy Department, University of Manchester, 
With 4 Figures. 
In recent observations on the position of the fingers in cases of 
ulnar and Kiumpxe paralysis, I have noticed that extension of the 
2nd and 3rd phalanges of the fingers, is not brought about by the 
action of the common extensor. As an instance of such cases, I quote 
the following: 
The patient, a girl of 23, had, in an accident, severed the ulnar 
nerve at the wrist. The extensor communis was of course unaffected, 
yet the patient was quite unable to extend the 2nd and 3rd phalanges 
of the middle and ring fingers, while her power over the index and 
little fingers was perfectly normal. 
In consequence of observations such as the above I was led to 
reinvestigate the action of the common extensor of the fingers, and 
also of the lumbricals and interossei, in view of their relation to 
extension of the digits. 
On reading the accounts given by various standard text books, 
(1) the following views are to be found regarding the insertions of 
the above muscles. 
(i) The extensor communis forms, on the dorsum of the first 
phalanx of each finger, an expansion which receives the lumbrical 
and interosseous tendons, and which divides into three slips. The 
median of these is inserted into the base of the second phalanx whilst 
the two lateral portions reunite, and pass to the base of the third 
phalanx. 
(ii) The lumbricals, interossei, and extensores indicis and minimi 
digiti are inserted into the “dorsal expansion” and into certain bony 
points which will be enumerated in the following pages. 
Anat. Anz. Bd. 42. Aufsätze. 10 
