178 NATURAL HISTORY SOCIETY OF DUBLIN. 
tensors and flexors, one for each, and likewise two pair of lateralizers 
in the form of interossei. 
Now, the muscles in question afford to us a very good example— 
the first of the extensor tertii internodii digitorum, and the second of 
the extensor secundi internodii digitorum. 
The flexors of the pes likewise afforded some interesting arrange- 
ments: the flexor hallucis gave off four tendons, and was joined at its 
point of division by the flexor digitorum and the massa carnea accesso- 
rius; from this conjoined source five tendons arose, one large slip to 
hallux, whose fibres arose mainly from the first-named tendons to the 
second, third, and fourth conjoined, composed of mixed threads from 
the first and second, and a fifth tendon derived entirely from the first. 
Professor Haughton, in speaking of this muscle, says that the flexor 
hallucis is analogous to the flexor profundus in the hand, and that the 
digitorum communis was inserted into the point of junction of the ac- 
cessorius and flexor hallucis longus, and mentions that the tendons of 
this muscle were chiefly distributed to the hallux and index. In my 
specimen, however, scarcely any of the flexor digitorum was continued 
into the halluceal tendon. However, this is an important point, for as I 
have elsewhere showed the true cause of the constant junctions of these 
two muscles depends upon the altered disposition of the lower limb 
bones, which necessitate a crossing of the muscles, when, according to a 
law of vital affinity, union occurs, as it almost invariably is liable to do 
in similar cases. Of the other muscles, I may mention that the pyri- 
formis and gluteus medius are closely united; the plantaris is large 
and distinct; the peroneus quinti digiti is very large and separate. 
This muscle, I find, has been called extensor minimi digiti by Professor 
Haughton—a name calculated to mislead as to the affinities of the 
muscle, though strictly correct as far as its use is concerned, for it is 
truly the representative of the ulnaris quinti digiti of the forearm, the 
occasional continued slip of the extensor carpi ulnaris to the first pha- 
lanx of the little finger, and it is very often present in the leg of a man 
as a slip of the peroneus brevis. It differs from the extensor in not run- 
ning in an extensor groove, but in the same sheath as the peroneus. 
The true extensor minimi digiti has been thrown back three stages in its 
insertion, and appears as the so-called peroneus tertius, which is some- 
times, though rarely, continued forwards into the extensor aponeurosis 
of the toes in man. 
Among the muscles of the trunk, a large trachelo-acromial is one of 
the most remarkable. This muscle appears sometimes to be doubled, 
as Professor Haughton notices it under the name of omo-atlanticus, 
Nos. 1 and 2. I did not find it double in either of my specimens. 
This muscle is of the same type as the levator clavicule of monkeys, or 
the masto-humeralis of cetaceans, and is the altered upper limb homo- 
type of the pyriformis. 
