NOTES AND MEMORANDA. 
251 
in determining the mode of nerve termination in the unstriated museles. 
In the voluntary unstriated muscles of the gasteropod mollusca (Helix 
pomatia'), the motor nerves are divided and subdivided apparently into 
tibrillae, which are lost at the surface of the muscular cells by expanding 
and forming a terminal arborisation, diminutive and badly defined, to 
which may be given the name of motor plate {tache motrice). In the 
unstriated and voluntary muscles of the gasteropods there are no anasto- 
moses between the motor nervous fibrillgB ; and henceforth a terminal 
nervous network cannot be admitted in their case. Amongst the 
mammals, batrachians, reptiles, and annelids, on the contrary, have been 
observed, in the organic unstriated muscles, a very complex nervous 
network, but branches of this network disengage themselves from the 
fibrillas, mostly very short, which are lost at the surface of the 
muscular cells, there expanding, and forming an arborisation less 
clearly defined and still smaller than in the muscles of the gasteropods. 
From this somewhat summary explanation — sufficient, however, for 
what I wish to present to-day — it results that (1) In the unstriated 
muscles the nerves terminate, as in the striated muscles, at the surface 
of the muscular elements by an expansion, more or less arborised, of 
the cylinder-axis. (2) The nervous network of the involuntary un- 
striated muscles is in connection, not with the elementary nervous 
action which sets the muscle in activity, but with a more complex 
action on which depends the functional energy of an organ whose 
activity is derived from the direct action of the nervous centres. In 
support of this point I may refer to the fact that the muscular 
coat of the oesophagus of the mammals, which is formed in great 
part of striated bundles, but which does not contract under the direct 
influence of the will of the animal, possesses a plexiform nervous 
apparatus, and that an apparatus of the same kind appears on the 
striated musculature of the digestive tube of the anthropods. 
It is scarcely necessary now to point out why the different authors 
who have studied the termination of the nerves in the unstriated 
muscles, in the different organs and in the different animals, have 
debated whether the termination is by free extremities or by networks. 
These networks exist, but in reality they constitute simple plexuses, 
from which the terminal fibrillge disengage themselves. 
Cover Adjustment for Microscope Objectives . — The present mode of 
correction adjustment fulfils its purpose only within narrow limits, 
and beyond these, various secondary faults appear which seriously 
deteriorate the performance of even otherwise most excellent ob- 
jectives. 
The cause of this imperfection lies in the circumstance that the 
change in relative distance of the lenses composing the objective, by 
which the adjustment for cover thickness is at present sought to be 
effected, affects principally the chromatic aberrations, while the optical 
influence of the covering glass preponderatingly disturbs the cor- 
rection of the spherical aberration. For instance, if both aberrations 
of an objective are corrected in the best manner for such rays as are 
reflected from an uncovered object, these rays will, as soon as the 
object is placed under a cover-glass, suffer from a spherical over- 
T 2 
