( 667} 
of the well known ,forced” vibrations under the influence of a 
constant impulse. 
Finally we have to take into consideration the fact that sometimes 
only very intensive stimuli cause rhythmic effects, often accompa- 
nied by a rather important deformation of the one-termed sinusform. 
This might tend to indicate that the simple proportionality 
of the deviation and the stimulus no longer existed, and that we 
ought therefore to add higher terms. The phenomena, possibly 
belonging to this series, are besides the different tremores ihe 
rhythmical contractions of the apex of the heart in absence. of 
nervous ceils, rhythmical muscle-contractions by galvanic stimulation 
and many others. 
All these questions will be made the object of later researches. 
Though in the foregoing only the crude outlines of a provisory 
sketch have been given, I yet believe myself justified in publishing 
them. For by means of my theory a great number of facts 
are combined to one group, and it tends to show how these 
many different functions, apparently so widely divergent, may still 
be considered from one point of view; how notwithstanding 
their apparent complete incongruity, there still exists one com- 
mon ground, one and the same basis on which they all together 
are founded. 
Chemistry. — „On the decomposition of mercury nitrates by 
heating.’ By Dr. J. Mrsers of Hoorn (Communicated by 
Prof. BAKHUIsS ROOZEBOOM). 
(Communicated in the meeting of March 29, 1902). 
When crystallised. mercurous nitrate, either the normal compound 
or one of the basic salts, is heated in a retort which is connected 
with suitable apparatus to collect or condense the gaseous products, 
the apparatus nearest to the retort will be found to contain coloured 
HNO,, the condensing tube will contain an indigo-blue liquid con- 
sisting of N,Os and NO, while on continuing the decomposition NO 
is given off. If the anhydrous salts are taken, nearly pure NO, is 
condensed, but as it is difficult to expel the last traces of water a 
little coloured HNOs is also formed. 
