284 Royal Society : — 



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



of the same. 



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 hi a IVallahy 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 H.M.S. 'Lightning' in 

 the autumn of the year 1868, the dredge brought up, on the 6th of 

 September, from a depth of 530 fathoms, in lat. 59° 36' N., and 



