118 PATHOLOGY. 



perceptible protrusion of the nose ; indeed, in bronchitis, stupor 

 is present to such a degree tliat the animal generally hangs its 

 head. The functions of the body together gradually failing, the 

 symptoms of suffocation are less decided. 



The pathology of this mode of dying is now pretty well 

 understood. Bicliat made several experiments which went to 

 prove that unaerated blood not only reached the left side of the 

 heart, but was sent to all the arteries of the body. 



His experiments were as follows: — A ligature was applied to 

 the trachea of a living animal ; a small opening was then made 

 in one of the carotid arteries. Presently the slender stream of 

 l)lood which issued began to lose its arterial tint, and to assume 

 the dark colour of venous blood ; but, contrary to what had been 

 previously supj)Osed — namely, that the circulation would be 

 immediately arrested in the lungs, tlie quiescence of the lungs, 

 consequent upon the cessation of the alternate movements of 

 the thorax, forming a meclianical impediment to the transit of 

 blood through them (Haller), or that the unaerated blood passed 

 through the lungs and entered the left auricle and ventricle, but 

 went no farther (Dr. Godwin) — Bichat discovered that the 

 blood continued to flow from the opened carotid, and that its 

 afflux upon the brain was marked by convulsions and insensi- 

 l)ility. This led him to believe that the blood underwent no 

 obstruction in its passage through the lungs, but that, remaining 

 unpurified and venous, it acted as a poison upon every part to 

 which it was carried by the arteries — first upon the nervous 

 system, and ultimately (passing through the coronary arteries) 

 upon the muscular substance of the heart itself. " There are, 

 however," says Watson, " two well-known facts upon which this 

 theory is inexplicable — tlie comparative emptiness of the left 

 chambers of the heart, and the restoration of the suspended 

 functions by the timely performance of artificial respiration. 

 The air could never reach and revivify or depurate the venous 

 blood stagnating in the capillaries of the heart." Sir James 

 Kay Shuttleworth, in his work on Asphyxia, and later, Mr. 

 Erichsen, in the JEdinhurgh Medical and Surgical Journal, have 

 endeavoured to prove that stagnation of the blood commences 

 in the pulmonary capillaries, that the stagnation is due to its 

 non-arteriahzation, and that the movements of the left side of the 

 heart are brought to an end principally by the deficient supply 

 of blood from the lun<:s. 



