MUSCULAR METABOLISM DURING CONTRACTION 463 



continuance after sudden death from acute diseases. In some cases of sudden 

 death from lightning, violent injuries, or paroxysms of passion, rigor mortis has 

 been said not to occur at all ; but this is not always the case. It may, indeed, 

 be doubted whether there is really a complete absence of the post-mortem 

 rigidity in any such cases; for the experiments of Brown-Sequard make it 

 probable that the rigidity may supervene immediately after death, and then 

 pass away with such rapidity as to be scarcely observable. 



The occurrence of rigor mortis is not prevented by the previous existence 

 of paralysis in a part, provided the paralysis has not been attended with very 

 imperfect nutrition of the muscular tissue. 



The rigidity affects the involuntary as well as the voluntary muscles r 

 whether they be constructed of striped or unstriped fibers. The rigidity 

 of involuntary muscles with striped fibers is shown in the contraction of 

 the heart after death. The contraction of the muscles with unstriped fibers 

 is shown by an experiment of Valentin, who found that if a graduated tube 

 be connected with a portion of intestine taken from a recently killed animal, 

 and the intestine be tied at the opposite end, and filled with water, the water 

 will in a few hours rise to a considerable height in the tube, owing to the con- 

 traction of the intestinal walls. It is still better shown in the arteries, of 

 which all that have muscular coats contract after death, and thus present the 

 roundness and cord-like feel of the arteries of a limb lately removed, or those 

 of a body recently dead. Subsequently they relax, as do all the other mus- 

 cles, and feel lax and flabby and lie as if flattened, and with their walls nearly 

 in contact. 



Muscular Metabolism During Contraction. The question of the 

 metabolism of muscle both in a resting and in an active condition has for 

 many years occupied the attention of physiologists. It cannot be said even 

 now to be thoroughly understood. Most of the facts with reference to the 

 subject have been already mentioned. We may shortly recapitulate them 

 here : First, muscle during rest absorbs oxygen and gives out carbon dioxide. 

 This has been shown by an analysis of the gases of the blood going to and 

 leaving muscles. During activity, e.g., during tetanus, the same interchange 

 of gases takes place, but the quantities of the oxygen absorbed and of the 

 carbon dioxide given up are increased, and the proportion between them is 

 altered thus : 



