ANIMAL MECHANICS. 



73 



Other observers (Rosenthal) have found, as the maximum 

 force of the gastrocnemic muscles of the frog, from 1000 to 

 1200 grms., corresponding to a coefficient of contraction of 

 muscle, per centimeter of cross section, of from 1.8 to 3 

 kilograms per square centimeter. 



Mr. Baxter's average result given above corresponds to a 

 similar coefficient per square centimeter of only 371.51 grms. 



Borellihas given* many estimates of the force of the flexors 

 of the forearm, leg, jaw, and other muscles ; but as these esti- 

 mates are open to several objections, as well as his measure- 

 ments of the lengths of the arms of the levers engaged, I must 

 refer the curious reader to his original Propositions, which 

 may be justly regarded as a remarkable attempt, considering 

 the imperfections of the mechanical philosophy of his time, 

 to anticipate the more precise results demanded of animal 

 mechanics in our own day. The following remarks may be 

 made upon Borelli's observations : — 



1 . He has not been sufficiently careful to avoid the action 

 of muscles different from those supposed to be exclusively 

 employed. 



2. He has not measured, with sufficient care, the arms of 

 his levers. 



3. He has committed the common error of doubling the 



* De Motu Anirnalium Pars prima, Props, xxii. ... xxvii. Props, xl. 

 xli. liii. lxxxvii. lxxxviii — Rome: 1680. 2 vols. 8vo. 



I assume the pound used by Borelli to be 5000 grs., for the following rea- 

 sons : — 



The Cantaro piccolo is 106 lbs. av., or 150 lbs. of 12 oz. each; this would 

 give 4957 grs. to the Neapolitan pound. 



Gold and silver, in the time of Borelli, were weighed by a pound of 

 4950 grs. 



The Roman pound was 5234 grs. 



There is some difficulty in ascertaining what pound was used by Bo- 

 relli, but it is clear that it did not differ much from 5000 grs., and was there- 

 fore f ths of the pound avoirdupois. 



