CHEMICAL CONSTITUTION AND PHYSIOLOGICAL ACTION. 713 



that obtained from Mr Morson ; and as these, therefore, represent the extremes 

 among our samples, we shall describe in detail their action only. 



Our experiments were made with the hydrochl orate, which we obtained as a 

 nearly colourless, imperfectly crystalline, and deliquescent substance. The differ- 

 ence of activity between the hydrochlorate of Dr Christison's conia and that of 

 Mr Morson was so great, that while two-tenths of a grain of the former speedily 

 caused death in a full-grown rabbit, this dose of the latter did not produce any 

 distinct effect, one grain being the smallest fatal dose for a rabbit. The symptoms 

 that are produced in mammals by the different samples are very similar in 

 character. The more prominent of these are stiffness of the limbs, causing 

 difficulty in moving about ; spasmodic starts ; distinct increase of reflex excita- 

 bility; gradually increasing paralysis, with diminution, and, afterwards, dis- 

 appearance of the increased reflex excitability ; and, finally, death by asphyxia. 

 The exact causation of the paralytic symptoms differs, however, in a remarkable 

 manner in different samples of conia ; and the nature of this difference will be 

 shown in the detailed descriptions that follow. 



We shall consider, in the first place, the action of hydrochlorate of Dr Christi- 

 soy's conia. The following experiment illustrates the symptoms in mammals. 



Experiment LIV. — Two-tenths of a grain of hydrochlorate of Dr Christison's 

 conia, dissolved in four minims of distilled water, was administered by sub- 

 cutaneous injection to a rabbit, weighing three pounds and six ounces and-a-half. 

 In two minutes and thirty seconds, the limbs became somewhat stiff and 

 abnormally extended, so that the body was raised and an awkward posture 

 assumed. In three minutes, a slight touch of any part of the skin caused a 

 sudden spasmodic start ; and soon after a series of starts in rapid succession 

 occurred spontaneously, during which the limbs were still stiffly extended. 

 In eight minutes, these starts ceased, and the limbs assumed a nearly normal 

 position ; but the rabbit had now considerable difficulty in moving about, the 

 limbs being slightly paralysed. In sixteen minutes, the rabbit lay down and 

 rested in a crouching attitude, on the abdomen and chest. Soon after the neck 

 muscles were unable properly to support the head, which frequently subsided 

 on the table ; but there was now no distinct evidence of exaggeration of reflex 

 activity. In twenty-five minutes, the paralysis was so decided, that even a 

 sitting posture could not be maintained, and the rabbit lay on the side. The 

 respirations were infrequent and laboured, while common sensibility seemed to 

 be unimpaired, and the heart was ascertained to be contracting with nearly 

 normal force and rapidity. In twenty-eight minutes, some convulsive movements 

 occurred in the body and limbs, and now the respirations were so weak as to be 

 scarcely observable. The convulsive movements continued for other two minutes, 

 but at the end of this period they consisted of extremely feeble spasmodic starts. 

 In thirty-one minutes, the sensibility of the conjunctiva and cornea had dis- 



VOL. XXV. PART II. 8 Z 



