PHYSIOLOGICAL ACTION, AND ANTAGONISM. 
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It is occasionally increased by sodium, but is otherwise unaffected, excepting in 
large doses, and it is diminished almost invariably by lithium. 
The duration of the contraction, as shown by the length of the curve, is increased 
by large doses of rubidium (Plate 8, fig. 8, a, b, c ), ammonium (Plate 8, fig. 9, 
a, b), sodium (Plate 8, fig. 10, a, b, c ), and caesium (Plate 8, fig. 11, a, b). It 
is shortened by ammonium (Plate 8, fig. 12, a, b), lithium (Plate 8, fig. 13, a, b), 
rubidium, and potassium (Plate 8, fig. 14, a, b, c ). It wfill be seen from this 
enumeration that rubidium, ammonium, and sodium have a double action, sometimes 
increasing and sometimes diminishing the length of the contraction. In the case 
of rubidium and sodium the difference of action depends upon a difference of dose, 
small quantities tending to shorten the contraction, while large doses lengthen it. 
Prolonged contraction is accompanied, as we have already mentioned, by an increase 
of contractility in the case of rubidium, but by a diminution in the case of sodium, as 
shown by the height of the curve. The double action of ammonia does not seem to 
us to depend entirely on difference of dose, but rather to the ammonium having- 
two different kinds of action. 
The residual shortening, viscosity, or contracture, which sometimes succeeds an 
active contraction, is increased by large doses of rubidium, ammonium, lithium, 
and sodium. It is diminished by rubidium in small doses, ammonium, caesium, 
and potassium. Here, again, the different action of ammonia does not appear to us 
to depend entirely on difference of dose. 
Its double action appears to form, to a certain extent, a connecting link between 
the action of some members of the alkali group, such as potassium, and that of 
members of the group of alkaline earths. 
The relations between the various members of the present group have to be 
considered more fully in a subsequent section, because we find that some members 
of it, while having a somewhat similar action on normal muscle, will yet antagonise 
each other’s action, and although either of them given alone will lengthen the muscular 
curve, the lengthening will be abolished, and the curve reduced to the normal, by the 
administration of the two together. 
Action of Substances belonging to the Group of Alkaline Earths 
and Earths. 
The metals which we have examined belonging to the group of alkaline earths are 
calcium, strontium, and barium; and to that of the earths beryllium, yttrium, didy- 
mium, erbium, and lanthanum. The first three are dyads. Beryllium is also a dyad. 
The atomicity of the last four is not determined. Possibly they are all triads, though 
lanthanum has been grouped by Mendelejeff amongst the tetrads. The first point 
of difference that we notice about this large group is that it may be subdivided into 
