284 



Royal Society 



Cross sections of Muscles and Tendons in a Pyrenean Mastiff, and ratioi 



of the same. 



Name of muscle. 



1. Gastrocnemius 



2. Fl. carp, rad 



y. Fl. dig. long 



4. Ext. carp, rad 



5. Fl. carp, uln 



6. Fl. ball. long. 



7. Biceps humeri 



8. Fl. dig. sub! 



9. Fl. dig. prof 



10. Ext. cai'p. uln 



Cfoss section of 



muscle, in 

 square inches. 



2-631 

 0-283 

 0-195 

 0-632 

 0-176 

 0-680 

 0-909 

 0-319 

 0-902 

 o-i8i 



Cross section of Ratio of cross 



tendon, in (section of muscle 

 square inches, to that of tendon. 



0-0520 

 0-0059 

 0-0045 

 0-0160 

 0-0056 

 0-0228 

 0-0449 

 0-0251 

 0-0830 

 C-0197 



50-6 

 48-0 

 43-3 

 39-5 

 314 

 29-8 

 202 

 12-7 

 10-9 

 9-2 



These results, obtained from measurements made upon a freshly 

 killed animal, confirm those found from observation of the human 

 subject, and prove that the ratio of the cross section of the muscle 

 to that of its tendon depends upon the amount of friction experienced 

 by the latter, the coefficient being greater in proportion as the fric- 

 tion is less. 



The following observations, made upon a Wallaby Kangaroo, con- 

 firm in a general way the preceding results :— 



Cross sections of Muscles and Tendons in a Wallaby Kangaroo, and ratios 



of the same. 



It appears from the preceding investigation that the cross section 

 of a muscle does not bear a constant ratio to the cross section of 

 its tendon, unless the friction experienced by the muscle and tendon 

 be also constant, and that there may even be a surplusage of strength 

 in the tendon beyond what is absolutely necessary to resist the com- 

 bined force of the muscle and friction. This surplusage, however, 

 cannot be supposed to be large, if the principle of economy of material 

 in nature be admitted. 



"On Holtenia, a Genus of Vitreous Sponges." By Wyville 

 Thomson, LL.D., F.R.S,, Professor of Natural Science in Queen's 

 College, Belfast. 



During the deep-sea dredging cruise of II. M.S. 'Lightning* in 

 the autumn of the year 1868, the dredge brought up, on the (ith of 

 September, from a depth of 530 fathoms, in hit. 59° 30' N., and 



