212 J)r. Williams on the Cause and Effects of [Sept. 



and from its supply from llie thoracic duct being unassimilated), 

 could not pass from the pulmonary artery into the pulmonary 

 veins, without first being acted upon by pure atmospherical air. 

 As such a cause seemed likely to offer a solution for every phe- 

 nomenon connected with the subject, the idea was cherished, and 

 for further satisfaction, the following investigations were insti- 

 tuted on the canine species. An animal was destroyed by securing 

 the trachea at the acme of inspiration, afterwards the sternum 

 and cartilaginous ends of the ribs were removed. The blood 

 appeared norid in the pulmonary veins, and in the coronary 

 arteries through the pericardium. When the contractions of the 

 left ventricle began to flag, the pulmonary veins became less and 

 less distended, the blood changing from the florid to a darker 

 and darker colour as the currend diminished. At the last con- 

 traction the veins flattened, and the left ventricle felt contracted. 

 At this instant, an irregular or fluttering contraction of the mus- 

 cular fibres of the right ventricle commenced, and continued for 

 a short time, excited seemingly by the stimulus of distention, 

 from the accumulation of blood in its cavity. After the irregu- 

 lar muscular action had ceased, the right ventricle felt soft and 

 distended, the left was still contracted, but not so rigid as imme- 

 diately after the last systole. The pulmonary veins appeared 

 empty ; one of them was opened, when only a temporary oozing 

 of blood followed. The pericardium was then slit open, and the 

 right ventricle soon became enormously distended, yet no blood 

 flowed out of the punctured vein. Another pulmonary vein was 

 opened, followed by a similar oozing of blood. The pulmonary 

 artery was now punctured, and instantaneously the blood gushed 

 out, and deluged the shell of the chest. An animal was exa- 

 mined in the presence of Dr. Traill, after being destroyed in the 

 same manner as the above, and the pulmonary veins were found 

 in the same empty condition after the last systole. 



From the investigation, the following corollaries are drawn : 



1. That the blood is obstructed in its passage through the 

 lungs, on suspension of respiration, while its circulation through 

 the other parts of the body continues. 



2. That the obstruction of the blood in the lungs, on suspen- 

 sion of respiration, is not the effect of a mechanical cause. 



3. That the obstruction of the blood in the lungs, on suspen- 

 sion of respiration, arises from a deprivation of pure atmospheri- . 

 cal air. 



4. That the blood which is found post mortem in the left auricle 

 and ventricle, is the remnant after the last systole, and the sub- 

 sequent draining of the pulmonary veins. 



5. That the obstruction of the blood in the lungs, on suspen- 

 sion of respiration, is one of the principal causes of the vacuity 

 of the system circulating arterial blood post mortem. 



6. That the immediate cause of the cessation of the action of 



