ANIMAL MECHANICS. 



11 



Let P denote the weight employed, and Q the weight of 

 the criminal ; let e denote the coefficient of elasticity of the 

 rope used, and Fthe velocity acquired by the weight Q in 

 falling through the height h. 



If we consider the problem of the weight Q moving with 

 the velocity V, arid causing the weight P to move through 

 the intervention of the rope, whose elasticity is e ; the shock 

 produced on Pat the moment when the " chuck" takes place 

 is similar to that which occurs in the collision of bodies striking 

 each other, and is measured by the vis viva lost during their col- 

 lision. The vis viva lost during the shock is, by equation (2), 



but, since the work lost is half the vis viva lost, if we substitute 

 for V 2 its value, igh, we find 



Work lost = -^^( 1 (3) 



For the ropes usually employed, e may be considered as a 

 very small fraction, and e 2 may be totally disregarded. The 

 work lost is expended in causing shock to the neck, and should, 

 as I have already stated, be equal to at least 2240 foot lbs. 



In a case of hanging that came under my own observa- 

 tion, the criminal weighed 160 lbs., and was allowed to fall 

 through 14 ft. 6 in., which, allowing for some elasticity in the 

 rope, would correspond with 2240ft. lbs. of shock; in this 

 case, the anterior articulating surfaces of the second vertebra 

 were fractured near their posterior border (the fracture of 

 the bone extending to the foramina for the vertebral ar- 

 teries), but the odontoid process of the axis was not broken, 

 nor the transverse ligament of the atlas torn across. Death 

 in this case was as instantaneous as it would have been had 

 the transverse ligament given way, instead of the bone ; for 

 the shock reached the medulla, and its consequence was 



