has been stated, it is open to grave doubt whether reflex 

 vagal inhibition per se — that is, without the supervention of 

 fibrillation — is responsible for many deaths. Blocking of 

 the mitral orifice by a thrombus and embolism of the pul- 

 monary artery are known to be of very rare occurrence. 

 (Thrombosis and embolism of the coronary arteries kill, as 

 has been already stated, by fibrillation.) 



The old idea of a heart that is working with fair efiiciency 

 abruptly " failing to contract " against excessive resistance 

 may be set aside as untenable, in the absence of the sudden 

 action of violent poisons, etc. 



There remains the conclusion that the great majority of 

 absolutely sudden deaths are to be ascribed to ventricular 

 fibrillation. 



Symptoms of Ventricular Fibrillation in Man and 

 Animals. 



The similarity between the group of symptoms associated 

 with many cases of sudden death in man and those attendant 

 on ventricular fibrillation experimentally induced in animals 

 is indeed striking. The abrupt abolition of pulse, cardiac 

 impulse, and heart sounds, the sudden fall of blood pressure, 

 unconsciousness, muscular relaxation often preceded by a 

 brief phase of rigidity or convulsive movement, dilatation of 

 the pupils, and the continuance of slow deep respiratory 

 movements, are identical in animals and in the human 

 subject, while in the latter the speedy replacement of the 

 initial intense pallor by lividity or marked cyanosis is a 

 notable feature. The amount of colour in the face, together 

 with the occurrence of several respirations after the collapse, 

 have sometimes made onlookers somewhat incredulous that 

 death has taken place. The occurrence in some cases of 

 premonitory features such as extra-systolic irregularities, 

 bouts of tachycardia, etc., is significant. It is important 

 that, in the collection of evidence as to unexpected and 

 unexplained death, special attention should be devoted to 

 ascertaining the occurrence of the group of associated 

 features just stated; these have been very definitely recog- 

 nized in many cases of sudden death where accurate observa 

 tions have been made. Some such cases have come under 

 the direct observation of the writer. 



No doubt some of these phenomena are common to certain 

 other forms of sudden circulatory failure — for example, from 

 heart-block, collapse induced by violent afferent impulses 

 (blow on epigastrium, etc.), or in certain cases of auricular 

 flutter, etc. But there are special features in some of 

 these — for instance, as regards the behaviour of the 

 respiratory centre, etc. 



Protective and Bemedial Agencies. 

 In animal experimentation — on cats, which are remark- 

 ably liable to ventricular fibrillation — the use of certain 

 drugs has been found by the present writer*' (working in 



