318 PROTEIN POISONS 



"The changes which the heart undergoes, following the 

 increase in systole described, consist in a weakening in both 

 chambers, while the extent of dilatation may be still further 

 increased, or it may show little change. Two factors come 

 in to complicate the changes produced by the poison. First, 

 the great fall in blood pressure produced by it decreases 

 the resistance against which the heart has to contract; and 

 second, the changes in respiration, which at times produce 

 a mild degree of asphyxia. It happened in some cases, 

 before the poison was given, the artificial, respiration had 

 seemed entirely adequate, after its administration the 

 lungs did not inflate so well and the blood showed signs of 

 deficient aeration. The heart changes were therefore studied 

 further in animals in which all other organs, save the lungs, 

 were excluded from the circulation. This experiment was 

 carried out on a large bulldog anesthetized in the usual 

 way. Under artificial respiration the sternum was cut 

 lengthwise, the two halves pulled apart, and the heart 

 exposed. The large vessels at the base of the heart were 

 dissected free and a clamp placed in position on the aorta 

 just below the origin of the left subclavian artery, this and 

 the right subclavian being tied. A loose clamp was also 

 placed on the inferior vena cava just above the diaphragm. 

 Cannulas were placed in both common carotids and external 

 jugular veins. The cannulas in the left carotid and the 

 right jugular were paraffined and connected by a short 

 paraffined rubber tube, thus providing a channel for the 

 blood from the left to the right heart. The cannula in the 

 right carotid was connected with the mercury manometer to 

 record the blood pressure, and that in the left jugular was 

 used to inject the poison. The clamps on the aorta and 

 the vena cava were now closed, thus shutting off the circu- 

 lation in all parts of the body, except the heart and lungs. 

 The pericardium was opened and sewed to the sides of 

 the chest to form a sort of cradle for the heart. The myo- 

 cardiograph was attached to the right auricle and ventricle 

 in the usual manner, and arranged to record their move- 

 ments on the kymograph." After recovery from the opera- 



