OF THE CALABAR BEAN. 755 



that are still in connection with the great exciter ganglia in the auriculo-ven- 

 tricular septum will continue their spontaneous movements. 



The action is not a very powerful one, and its characteristics may be explained 

 because of that ; for the effects of physostigma on the heart appear to be similar to 

 those of weak forms of at least two of the ordinary cardiac poisons — of digitaline 

 in minute doses, and of the alcoholico-aqueous extract of Nerium Oleander, which 

 is merely the green extract mixed with various impurities, without which it has 

 the ordinary actions of the larger class of those substances that affect the 

 heart.* 



ACTION ON THE BLOOD-VESSELS. 



The question of the action of Calabar bean on the condition of the vascular 

 system is intimately connected with that of the cardiac effects ; and must, there- 

 fore, be considered also, that we may complete the examination of the influence 

 of this substance on the circulation. For this purpose, I instituted two sets of 

 experiments. In the first (1), the blood-tension in the arterial and venous sys- 

 tems was observed ; and in the second (2), the calibre- changes of the smaller 

 blood-vessels and of the capillaries were investigated. 



1. Examination of the Blood-Tension, and of the Coincident Changes in the Cardiac 

 and Respiratory Movements, and in the Temperature. 



In these experiments, the tension in the arterial system was determined by 

 dividing one of the carotid arteries and connecting the end proximal to the 

 heart with a modification of Poisseuille's hsemadynamometer, in which two 

 indicating columns were connected with the reservoir. The tube of one of these 

 had an extremely small orifice where it dipped into the mercury, and it, there- 

 fore, registered the mean pressure only. The orifice of the other had the same 

 diameter as the rest of the tube, and the contained mercury had, therefore, imme- 

 diately communicated to it every change of pressure, and oscillated synchronously 

 with the heart's beats. The venous pressure was ascertained by a simple hsema- 

 dynamometer having one registering column. The indicating columns were 

 divided into inches and tenths of inches. 



In the experiments where the temperature was observed, a delicate ther- 

 mometer was inserted into the subcutaneous tissue at the flank of the animal, and 

 retained there, under the charge of an assistant, during all the time of the expe- 

 riment. 



* Pelikan, op. cit., Comptes Rendus, 1866. 

 VOL. XXIV. PART III. 9 T 



