ZOOLOGY AND BOTANY, MIOEOSCOPY, ETC. 59 



of the forceps of the decapodous Crustacea ; Carcinus maenas was 

 found to adapt itself well to experiments of this nature ; Platycarcinus 

 pagurus and others were also used. 



The experiments were thus performed : a rectangular piece of 

 wood, pierced by several rows of holes, is suspended vertically by a 

 fixed support, and several holes are made near its superior edge ; the 

 crab is fixed on the board with its mouth downwards, in such a way 

 that the lateral regions of the sternal face of the carapace can be 

 conveniently got at ; the process of the propodite is superior and the 

 movable dactylopodite inferior. The crab generally keeps its forceps 

 closed; weights are then added till the forceps begin to open. To 

 greatly stimulate the animal and cause it to put into play its 

 maximum of muscular energy, a small stylet may be introduced 

 between the thorax and the abdomen ; the crab then closes its forceps 

 with great force, raises, and often holds up, the weight. The weights 

 are increased till the animal is only just able to raise the weight. 

 Suitable weighings are made, and the second forceps, if present, is, 

 after a short period of repose, experimented on in a similar fashion. 

 The crab is then weighed, chloroformed, and its forceps put for some 

 days in alcohol of 50 per cent. Though the action of the alcohol is 

 to somewhat reduce the volume of the muscular masses, the incon- 

 venience is atoned for by the facility with which one can make 

 transverse sections so as to measure the surfaces. Suitable measure- 

 ments having been obtained, the results are worked out; and it is 

 found that, for the common crab, 851 gr. (when large), or 961*6 gr. 

 (when smaller), are the mean weights, supported by a square cen- 

 timetre of the flexor muscle of the right forceps ; that of the left 

 gives, respectively, 1336 "7 gr. and 1181 '2 gr. 



When we compare the mean weight with that supported by other 

 animals, we find that crabs give us 1008*75, as against 2000 for the 

 frog, 4545*79 for the lamellibranchiate, and 7902*33 for man. It 

 follows then that the absolute or static force of the muscles of the 

 Crustacea is comparatively feeble. 



If we look at the matter in another way, and consider the question 

 of the muscular force of an animal without regarding either the 

 dimensions of these muscles, or the number of contractile elements 

 which enter into their composition, we get very different results. 

 Proportionately to their weight molluscs, insects, and Crustacea 

 have an enormous force, some much greater than that of mammals. 

 Thus the proportion of the weight carried to that of the body is, for 

 the horse * 50 to * 83 ; for man * 86, for Carcinus 5 * 57, for insects 

 from 14*3 to 23*5. A small number of special muscles give results 

 of the same kind — the force of the muscles of the forceps of the 

 common crab is forty times as great as that of the human hand. 



It is clear that we cannot allow that the force of contraction of 

 muscular fibre is the same throughout the animal kingdom. 



The author has made some experiments with reference to the 

 injuries which crabs can undoubtedly inflict on other animals, and he 

 comes to the conclusion that it is not necessary to suppose that the 

 Decapoda have any extraordinary force. 



