1568 
We wish to point out also that, taking into account the inevitable 
sources of experimental errors, we see a striking concordance in 
the results regarding respectively the left and the right triceps of 
the same animal. Only in ease VI there, was a marked difference; 
it should not be forgotten, however, that in this case we had to do 
with a cat that had been under the unfavourable influence of con- 
finement. 
We venture to assume that the observations communicated above 
confirm our previous hypothesis based on various experiments, viz: 
whereas a rapid contraction of the muscle is accompanied by a 
metabolic change of non-nitrogenous substances, with another action 
of the muscle fibres, the tonus, nitrogen-containing substances are 
katabolized, from which material kreatin originates. 
Physics. — “On the second virial coefficient for rigid spherical 
molecules carrying quadruplets’. By Dr. W. H. Kersom and 
Miss C. van Leeuwen. Supplement N°. 39¢ to the Commu- 
nications from tie Physical Laboratory at Leiden. (Commu- 
nicated by Prof. H. KAMERLINGH ONNES). 
(Communicated in the meeting of March 25, 1916). 
§ i. In Suppl. N°. 39¢ (Sept. °15) formulae were given which 
make it possible to develop into a series of ascending powers of 
Tt the second virial coefficient for rigid spherical quadruplets (mole- 
cules whose mutual attraction is equivalent to that of zonal quadru- 
plets placed at their centre). Of this series, which at the lower tem- 
peratures is but slowly convergent, a number of terms was calculated 
such, that the virial coefficient under consideration (4) could be 
derived with an accuracy of about 1°/, (of B) for temperatures 
down to °/, Tj» (oo). Subsequently these results were compared with 
the experimental data concerning hydrogen, down to about 150° K. 
We have now calculated some more terms of the series, so that 
it can now be used down to about '/, Tino(z=o), or for hydrogen 
down to about 96° K, with an accuracy which can be put at 1°/, 
of B. The whole region above the Boye point is therefore included. 
$ 2. Adding the new terms to those of equation (18) of Suppl. 
N°. 39 we obtain '): 
1) For the notation we refer to Suppl. N°. 39a. 
