The appendicular muscles of Necturus maculosus. 401 



-carpals are also preserved, and the beilies of the extensores breves are 

 described as accessory slips inserting into the under (ventral) surface of 

 the long tendons (Humphrey, Osawa). Eislee makes the short extensors 

 much more complicated, dividing them into three layers with different 

 conditions in the different regions, but OSAWA, who is not only the latest 

 writer on the subject, but who had the advantage of studying the large 

 C. japonicus in place of the much smaller C. allegheniense, which was the 

 one used by EiSLER, finds nothing of this, and describes them as simple 

 muscle bellies, with the relations as descrihed above for Necturus. 



2. Volar aspect offorearm and hand. 



Palmar fascia (fp). The muscles of the volar surface of the 

 forearm and hand are covered superficialry by a fascia which, distal 

 to about the middle of the forearm, becomes thick and opaque, 

 concealing all subjacent parts. This latter portion is the palmar 

 fascia proper, and extends distally as a continuous sheet from the 

 distal margin of M. palmaris superficialis, of which it forms an 

 aponeurotic continuation. At about the base of the metacarpals it 

 divides into four slips. which gradually narrow and lie along the 

 volar aspects of the four digits, inserting into the bases of the 

 terminal phalanges. These tendon-like strips are tied down by 

 Ligaments opposite the metacarpo-phalaugeal joints, and, in the case 

 of digit IV, opposite also the extra Joint between phalanges 1 and 2. 

 While opposite the row of carpalia, and shortly before its divi- 

 sion into the four digital slips, the palmar fascia becomes firmly 

 fastened to the distal border of these bones, and tlie crescentic 

 partition of firm connective tissue thus formed, and the surface of 

 the fascia adjacent to it distally, furnish the points of origin for the 

 two sets of short flexors of the digits. Proximal to this partition 

 the palmaris profundus becomes inserted into the dorsal (inner) sur- 

 face of the fascia. The entire set of muscles thus united into a 

 System through the medium of the palmar fascia includes both super- 

 ficial and deep palmar muscles, as well as the two sets of short 

 flexors, superficiales and profundi, and the whole acts as a Compound 

 flexor of the digits. 



Certain authors, including recent ones (Osawa), have considered the 

 digital portions of the fascia to be the tendons of a long flexor, the 

 palmaris superficialis being the muscular belly associated with it. That 

 the definite long flexor System of higher animals becomes derived from a 

 condition similar to that in Necturus, and that we have here such a System 

 almost begun, cannot be doubted, but in view of the complex relationship 

 of the fascia to many muscles it seems best to treat it as has here been 

 Zool. Jahrb., Suppl. XV (Festschrift für J. W. Spengel Bd. II). 26 



