PHYSIOLOGICAL ACTION, AND ANTAGONISM. 
215 
inclined to regard it rather as an indication of failing power in motor nerves than to 
increased irritability in nerve centres. 
Iodides. * 
As we have already shown in an earlier part of this paper, ammonium iodide has 
a powerful paralyzing action, both on nerve centres and motor nerves, producing 
sluggish movements and motor paralysis. 
From experiments on Frogs we find that methyl- (Plate 8, fig. 2, a, b), ethyl-, and 
am yl- (Plate 8, fig. 3, a, b, c) ammonium iodides all produce torpor. In the ethyl- 
ammonium iodide, Goltz’s “croak” experiment succeeded as it did in the case of simple 
ammonia iodide. With the amyl-ammonium iodide, jerking or staccato movement of 
the limbs was observed, apparently due to failure of motor power. The methyl-, 
ethyl-, and amyl-ammonium iodides in small doses increase the excitability both of 
nerve and muscle. In large doses they are powerful poisons to motor nerves ; they 
have a tendency to alter the formation of the muscle curve, and produce in it a 
curious hump, but they do not appear to affect muscle as much as nerve. 
The occurrence of the croak in the ethyl-ammonium iodide would appear to 
indicate rapid paralysis of the higher nerve centres; and the staccato movement in the 
amyl-ammonium iodide, more rapid failure of motor nerves. 
The dimethyl- and diethyl-ammonium iodides produced increasing lethargy, with 
no spasm ; with the diethyl-ammonium iodide the “ croak ” experiment succeeded, as 
it did with the ethyl-ammonium iodide. 
Their action upon muscle and nerve seems to be similar to that of the methyl- and 
ethyl-ammonium iodides. Trimethyl- and triethyl-ammonium iodides have an action 
like that of the dimethyl- and diethyl-ammonium iodides, but they appear to have a 
greater paralyzing action on muscle and nerve (Plate 8, fig. 4, a, b, c ), the primary 
increase in excitability not being marked, and paralysis of both occurring more readily. 
The tetramethyl- and tetraethyl- (Plate 8, fig. 5, a, b, c) ammonium iodides present a 
marked contrast to the other iodides, as Frogs poisoned by them exhibit spasmodic 
twitchings of the trunk and extremities. The higher reflexes cease very rapidly. The 
nerve is generally completeiy paralyzed. The muscle is only slightly affected when 
the poisoning is rapid, but if it be slow it is completely paralyzed also. 
All the iodides render the beats of the heart slow, and tend to produce still-stand 
in diastole. 
In the case of triethyl-ammonium iodide a vermicular movement of the heart was 
observed. 
The tetraethyl- and tetramethyl-ammonium iodides appear to have a more 
powerful action than the others in producing diastolic still-stand of the heart. 
