310 Dr. L. llogers. On the Physiological [June 6, 



Both the curves of the two experiments above detailed show the 

 same sequence of results, viz., primary failure of respiration accom- 

 panied by a rise of blood pressure, followed by a fall of the same 

 some little time after the respirations have entirely ceased. There is 

 one remarkable and important difference between them, namely, an 

 entire absence of respiratory convulsions in the case of the last very 

 rapid poisoning. This absence of convulsions may be due to the 

 respiratory centre being so rapidly overwhelmed by the relatively 

 enormous dose of poison injected direct into the circulation (for the 

 amount used amounted to some 200 times the minimal lethal dose for 

 a rabbit), that the centre was paralysed completely before the failure 

 of the breathing had had time to render the blood sufficiently venous 

 to produce respiratory convulsions. The comparatively slight rise of 

 blood pressure occurring with the failure in respiration in this case as 

 compared with comparatively large rise obtaining in the other four 

 experiments agrees with the explanation just suggested. 



Another possible explanation must, however, be considered; a 

 paralysis of the end plates of the motor nerves, which, as we shall 

 see presently is a marked feature of the action of the poison under 

 consideration, might cut off' the peripheral muscles from the action 

 of the respiratory centre, in spite of its over-stimulation by venus 

 blood. In order to test this possibility, the right leg, exclusive of the 

 sciatic nerve, was ligatured before the poison was injected in Experi- 

 ment 5, and the response of the nerves and muscles of both limbs to 

 the interrupted induced current was tested immediately after the death 

 of the animal, with the following result : 



Distance of Contraction 



secondary coil. of musrle. 



Protracted limb, nerve 45mm. Good. 



muscle 45 Good. 



Poisoned limb, nerve , , Nil. 



muscle 45 Good. 



Here we have a typical curara effect, the end plates of the poisoned 

 limb only being completely paralysed. In this experiment it is there- 

 fore impossible to say how far the absence of convulsions is due to this 

 cause and how far to failure of the respiratory centre. I shall return 

 to this point further on, after the experiments on the action of the 

 poison on the nerves have been related. 



Direct Action on the Heart. 



The next question to be dealt with is whether the poison of the 

 Enhydrina has any direct action on the heart, which is so marked a 

 feature in the case of Pseudechis poison,* and has also been noted in 

 * c Hoy. Soc. of New South Wales Proc.,' 1896. 



