PRODUCED BY ATROPIA IN COLD-BLOODED ANIMALS. 467 



abdominal cavity, but the small bulk of such a solution is also an advantage 

 when atropia is exhibited by injection under the skin. In the latter case, the 

 energetic movements that nearly invariably occur when the frog is set free, are 

 very apt to press some of the solution out of the subcutaneous tissue; and 

 even with this precaution I have found it difficult to prevent all loss. 



It appears from the experiments contained in Table I. that tetanus is also 

 pretty constantly produced by doses somewhat greater or less than the xoWth 

 of the weight of the frog; indeed, by the majority of the doses included between 

 the T^th and the x^Voth. The larger doses usually produce the most violent 

 tetanic symptoms, and they may be given with considerable confidence to very 

 small animals, and to such as have been kept in a laboratory for several months. 

 The smaller doses seem best adapted for large frogs, and for such as have been 

 recently obtained from their natural habitats. If a dose be employed smaller 

 than those above indicated, impairment of the functions of the cerebro-spinal 

 nervous system and of the heart may be caused, but general tetanus will seldom 

 follow, although spasms, generally restricted to certain regions, may occasionally 

 appear. The tetanic state resulting from the largest doses usually terminates in 

 death, that from the smallest in recovery. 



In the above Table, the smallest dose of sulphate of atropia that produced 

 tetanus is equivalent to the T^o^h of the weight of a frog of 298 grains (Experi- 

 ment v.), the largest to the y-lgth of the weight of a frog of 147 grains (Experi- 

 ment xxxviii:) 



Without attaching undue weight to an experience which is insufficient to 

 justify generalisation on such a subject, it may be mentioned that tetanic symp- 

 toms were usually produced most readily, and continued for longest periods, 

 in the experiments that were made in winter, when the temperature of the 

 laboratory was low. 



SECTION C. 



It is by no means an easy matter to ascertain what structures are concerned 

 in the production of the convulsant effects of atropia, for the protracted intervals 

 that often elapse between the administration of the poison and the appearance of 

 tetanus, and the difference in the duration and severity of the tetanic symptoms 

 that follow even the most carefully calculated doses, render the inquiry an unusually 

 difficult one, and frequently necessitate a patient repetition of the experiments. 

 It is obvious, at the outset, that experimental investigation is required. It cannot 

 be maintained that these remarkable convulsant and tetanic effects are merely 

 secondary results of certain degrees of the primary paralysing action of atropia 

 on the cerebro-spinal system and on the heart. Against such a supposition it 

 were easy to bring a mass of opposing evidence, derived from the physiological 

 effects of other active substances. It is well known that after the administration 



