Cunningham and Bkooks — The Peroneous Quinti Bigiti. 79 
and man the descent of the extensor brevis I.-IY. can be traced step 
by step. Pirst one belly descends, and then another, and so on until 
all the four tendons spring from fleshy bellies which lie on the dorsum 
of [the foot. But what becomes of the extensor brevis Y. ? It is left 
behind. A peroneus brevis is developed out of it, and ultimately in 
the higher forms, as in man, the offspring swallows up the parent ; in 
other words, the extensor brevis Y. is obliterated, and only occasionally 
appears in the form of the little tendinous slip which receives the name 
of the peroneus quinti digiti. 
With a history so interesting it is not surprising that the peroneus 
quinti digiti (or extensor brevis Y.) should have received so much 
attention from anatomists — an attention which, as we have already 
stated, is altogether unwarranted by its functional importance. 
Statistics of its relative frequency have been given by Pozzi ^ and 
Wood.^ The former anatomist examined 28 subjects, and found the 
muscle present in four cases, i. e. 1 in 7. Wood has published two 
series of statistics. In the first of these he only met with the 
peroneus quinti digiti five times in 32 subjects; but in his later, and 
more complete statistics, he states that he discovered it 36 times in 
102 subjects, i. ^. 1 in 3. 
Por two years we have kept an accurate record of the occurence of 
the peroneus quinti digiti in the Practical Anatomy Department of 
Trinity College. Forty -five lower limbs were specially examined, with 
a view of determining whether it was present or not. The following 
are our results : — 
Present in a well-marked form in 21 cases. 
,, rudimentary form in 5 ,, 
Absent in .... 19 ,, 
45 
In the cases indicated as "present in a well-marked form," the 
tendinous slip arose from the tendon of the peroneus brevis at some 
point between the maleolus and the projection on the base of the fifth 
metatarsal bone, and joined the dorsal expansion of the long extensor 
tendon of the little toe. In those cases indicated as rudimentary " 
2 Journ. de VAnatomie et de la Phijs.^ 1872. 
3 Froc. Roy. Soc. Zond., vols. xv. andxvi. 
