ARTIFICIAL RHYTHM. 207 
specimen both before and after the operation. The 
sketches are of life size, and drawn to accurate 
measurement (Figs. 29 and 30).* 
30. 
With regard to this remarkable effect on the 
manubrium of removing the margin of the necto- 
calyx, it is now to be observed that in it we 
appear to have very unexceptionable evidence of 
such a relation subsisting between the ganglia 
of the nectocalyx and the muscular fibres of 
the manubrium as elsewhere gives rise to what 
is known as muscular tonus. This interpretation 
* T may here mention that the fact of the manubrium of Sarsia 
undergoing this extreme elongation after the removal of the mar- 
ginal ganglia, serves to render the artificial rhythm of the organ 
under the influence of injury, as previously described, all the more 
conspicuous. 
