186 



DEPARTMENT OF THE XAVAL SERVICE 



are for the purpose of increasing the surfaces for the attachment of the muscle fibres. 

 The edges of the flat disc are thinner than the central portion, so that a cross-section 

 of the narrow end where there are no keels has very much the appearance represented 

 by figure 2. 



Fig. 2, Diagrammatic outline <yf the naked eye appearance of a cross-section of the flexor 

 tendon towards its narrow end, that is, the end which is distal to the dactyl. 



On the other hand a transverse section close to the ojiposite end shows a section 

 of one keel and of the two leaves of the disc. The reason that both keels do not show 

 is because one keel develops further back on the disc on one side than on the other. 

 Figure 3 illustrates the appearance of a transverse section from that end of a flexor 

 tendon which lies nearest the proximal end of the free dactyl. 



Pig. 3. A.B. represents cross-sections of the two keels, jvhile C represents a section of 

 the larger portion of the oval plate or disc; the smaller portion is out of the plane of section. 



Fig. 4. Represents the tip of a section of one of the keels at the end next to the dactyl. 

 This drawing is an enlarged one of figure 3 ,at A. 



When a cross-section of the disc is made at about one-quarter of its length from 

 the end next to the dactyl, the general appearance is that of a cross, because both 

 keels or ridges then come into view, as well, of course, as both halves of the oval 

 disc or plate. 



D 



B 



Pig. 5. Diagrammatic outline of the naked eye appearance of a cross-section of the flexor 

 tendon, at a short distance from -where it is attached to the free dactyl. A.B. upper and 

 lower keels; CD. larger and smaller portions of the oval disc or plate. 



