XVI. 



THE HISTOLOGY OF THE FLEXOR TENDON IN THE CRUSHING CLAW 



OF THE LOBSTER. 



By A. P. Km.;iit, M.A., M.D., F.E.S.C., 

 Emeritus Professor of Biologj/, Queen's University, Kingston, Ont. 



(■\Vitli S Figures.) 



" The crushing claw has a far more powerful musculature than its fellow, and 

 is accordingly richer in its supply of blood-vessels and nerves. Two tendons spring 

 from opposite sides of the proximal end of the free dactyl and afford a surface for ^ 

 the attachment of the huge flexor and smaller extensor muscles. Each tendon is a 

 keeled oval plate which is developed in a flattened pocket of the skin, but the closing 

 muscle of the great claw being the largest and the strongest in the body, requires the 

 largest tendon. The tendon of the flexor is a broad leaf-shaped plate, keeled above 

 and below, while that of the weaker opening muscle is narrow and strap-shaped. 



* * * * 



"At the time of moulting tlicse huge tendons, like all others in the body, are 

 withdrawn attached to the cast-ofl" shell, and leave deep open pockets into which, 

 in a large animal, the little finger can easily be inserted. As soon, however, as the 

 soft claw becomes tense with blood, the opposed surfaces of the muscle substance 

 unite and a new tendon is fnrmi'd at tho site of the old one." (From Dr. Herrick's 

 American Lobster.) 



Fig. 1. Gross appearance of the tendon viewed from such a position that both the upper 

 and the lower keels can be seen. A.B. section througrh both keels and one-half of the oval 

 plate of disc as shown in figure 3. P.Q. section throug-h both keels and both halves of the 

 oval plate as shown in figure 5. X.Y. section through the oval plate only as sliown in figure 2. 



It will I be remembered that the general outline of the tendon is that of a flat 

 oval-shaped disc. Along both its upper and its under surface a keel or ridge runs 

 from the broad end towards the narrow end for about half its length. These ridges 



79550—13 185 , 



