130 F. E. Nipher— Work done by a Muscle before exhaustion. 
I have received through Professor Baird, of the Smithsonian 
Institution, a pair of jaws and two large ‘suckers of the ong 
arms, which were taken from a specimen (No. 4), cast sohill 
in Bonavista Bay, Newfoundland. These jaws agree precisely 
in form and size with those described above, so that the size of 
these two individuals must have been about the same. The 
suckers (plate Iv, figs. 12, 13) had been dried, and have lost 
their true form, ut the marginal rings are perfect, and only “92 
of an inch in diameter, and though “somewhat smaller than in 
the specimen just described, they have the same kind of den- 
ticulation around the margin. Their smaller size may indicate 
that the specimen was a female, but they may not have been 
the largest of those on the arm 
EXPLANATION OF PLATES. 
Plate 1.—Figure 1. Architeuthis monachus Steenstrup (No. 5); sy natural size. 
Plate 11.—Figure 2. Anterior part of the “ pen ™ of the same; 4 natural size The 
otted lines indicate parts that are wanting 
tached 3. Upper j f the same; natural si 
re wer jaw of the same, lacking a a small piece at a. 
Plate rv. Stl 5 and 5a Jaws of Loligo age a, the rostrum or beak; 4 }, 
the cutting edge, with a notch at b; bc, the ey ed alee 
: the frontal lamina in the u jaw, or chin-portion 
(men the lower jaw; e, the palatine (anise in the upper jaw, 
or gular lamina in the lower jaw; twice th 
Figure 6. Part of the lingual ribbon of A. tee rh enlarged. 
Figure 7. SE Wl ES ida; much enla 
Figure 8. Ditto of Loligo Hartingii, copied from Harting; enlarged. 
Figure 9. Caudal fin of A. monachus (No. 5); >}; natural size 
Figure 10. Marginal mG of a sucker from one er the séoails arms}; 
enlarged two diamete 
Figure 11. a, A hes. Peta pe By _ ee 8 small marginal sucker from the 
mtacular a a; nat ural 
Figure 12. Srey jackie’ from porhafer arm of No. 4; natural size. 
Figure 13. Part of the marginal ring of the same; e' enlarged. 
[To be continued. ] 
Art. XVIL—On the Mechanical Work done by a Muscle before 
Exhaustion by. F. E. Nipwer, Assistant Professor of 
Physics in Was ington University. 
Tue work done by a muscle may be classed under two 
heads: 1st. The exerting of any force (F) through any distance 
(D). To distinguish this kind of work from the other, we may 
call it dynamical work. It is measured by the product FD. 
2d. Suppose an experimenter to hold a weight on his out 
pause arm, and suppose furthermore that the experiment 
is one of the weights of a large Atwood’s machine, and 18 
Guved vertically with an accelerated motion. The dy ‘namical 
work done by the arm before exhaustion is easily ‘obtain 
from the equations of dynamics. If now the acceleration be 
