[ 78 J 
XI. 
THE PEEOTTETJS QUHSTTI DIGITI. Et D. J. CUNlSriKGHAM 
(M.D. Edin. et Dubl.), Professor of Anatomy, Trinity College; 
and H. St. JOHI^ EROOKS, M. D., Dubl., Demonstrator of 
Anatomy, Trinity College, Dublin. 
[Read June 27, 1887.] 
This communication was suggested to us by tbe occurrence of two re- 
markably well-developed examples of the peroneus quinti digiti muscle 
in tbe Dissecting-room of Trinity College. The tendinous slip which 
bears this name is only occasionally present in the human foot. It is 
of little or no functional value ; but it possesses a high interest in con- 
nexion with the history of the peroneus brevis and extensor brevis 
digitorum muscles. In its most common condition this slender tendi- 
nous slip springs from the tendon of the peroneus brevis on the outer 
side of the foot, and proceeds forwards to the dorsum of the little toe, 
where it lies in series with the four tendons which the extensor brevis 
digitorum gives to the four inner toes. 
A few years ago Dr. George Euge ^ of Heidelberg proved in the 
most conclusive manner that the position of the extensor brevis on the 
dorsum of the foot is not primitive, but one which is acquired. 
Originally it was a muscle of the leg, and arose from the fibula along 
with the peroneal muscles. In the omithorhynchus it consists of two 
parts — (1) an extensor brevis of the four inner toes, to each of which 
it sends a tendon ; (2) an extensor brevis of the little toe. Eut 
further, the peroneus brevis can hardly be said to have any existence 
in this condition. It is merely represented by a small tendinous slip 
which proceeds from the tendon of the extensor brevis of the little toe. 
Erom this and other facts Euge comes to the conclusion that the 
peroneus brevis is to be regarded as an offshoot from the extensor 
brevis V. 
In the animal groups which intervene between the omithorhynchus 
^ Untersuchung iiber die Extensorengruppe am Unterschenkel und Fusse der 
Siiugethiere. — Morph. Jahr., 1880. 
